texts: Help with a reaction: naphthalic anhydride to diol with LAH

texts:
First time asking a question but I've been trying to perform this reaction:

for quite a while now. Most of the times I've only gotten this far:

Here is the procedure I've been following:
Dry THF (20 mL), LiAlH4 (6 mmol) and anhydrous ZnCl2 (3 mmol) were added in a 100 mL round‐bottom flask fitted with a CaCl2 guard tube and mounted over a magnetic stirrer. 1,8‐Naphthalic anhydride (0.99 g, 5 mmol) was added into the flask slowly at room temperature. After 6 hr, the excess LiAlH4 was destroyed by addition of 5 mL water, and the mixture was adjusted with 1 N HCl to weak acidity. The resultant two‐phase solution was extracted with ethyl acetate (3 × 15 mL), washed with brine and then dried over anhydrous MgSO4. After the solvent was evaporated, the crude product was recrystallized with benzene and methanol (1/1) to give white crystals 0.790 g (84.1% yield). M.p.: 161–163°C (lit.2c Boekelheide, B. and Vick, G. K. 1956. A synthesis of pleiadiene and acepleiadylene. J. Am. Chem. Soc., 78: 653
 [Google Scholar]
 157–158°C); ESI‐MS (m/z): 171 (M + H − H2O)+, 189 (M)+; IR (cm−1): 3345, 3241, 1601, 1510,1425, 1366, 1320, 1058, 1035, 1013, 998, 826, 774.724; 1H NMR (600 MHz, CD3COCD3), δ4.54 (s, 2H), 5.27 (s, 4H), 7.44 (t, 2H, J = 7.5 Hz), 7.64 (d, 2H, J = 7.2 Hz), 7.87 (d, 2H, J = 7.8 Hz).

from this paper:
https://www-tandfonline-com.proxy.bc.edu/doi/full/10.1081/SCC-120038510?scroll=top&needAccess=true

I've tried using ZnCl2, but it's hygroscopic so picks up water in the atmosphere and destroys my LAH (this is my hypothesis). I also tried refluxing for 8 hours and again only got the second product before my THF evaporated. Do you guys have any suggestions? Thanks in advance.


texts:
Firstly haworth used CH3I/Ag2O with glucose which replaced 5 H by CH3 forming a acetal which locked the anomer and stopped the equilibirium of ring chain tautomerism. Under dilute acidic conditions acetal group hydrolyze and ethers do not.

So my text (Organic chemistry by L.G. Wade 8th edition) says through these reactions haworth suggested that C5  contains free hydroxyl group and hence proved the pyranose(6 membered cyclic ring) form of glucose. But I fail to understand how did he find that the hydroxyl group is present on the 5th carbon in the chain after hydrolyzation by dilute acid.


texts: A bit of trouble I am having with grasping the concept of fischer projections for long chained molecules. Take any non-cyclic carbohydrate from a tetrose and upwards and make an actual model of it and what we see is that the carbon backbone follows a zigzag pattern. However, according to the fischer projections, if we take any chiral carbon the vertical bonds go into the plane of the paper and the horizontal out of the plane of the paper. With a real-life model which follows a tetrahedral structure at each carbon atom and a zigzag pattern this just doesn't seem to work. What is going on here??


texts: Recommendations for electrostatic potential surfaces

texts:
Are there standards for density cutoffs, colours and colour mappings for electrostatic potential surfaces?

I observe that people use many different values.
For instance, this article (in Fig. 1a) uses 0.001 au density cutoffs with colours ranging from blue (< 0 kcal/mol) to red (> 20 kcal/mol).

I understand that not every colour/energy range will work every time, but other publications/websites even switch the colour range.
This website, for instance, uses red for negative energies and blue for most positive ones.
Furthermore, the same website suggests a .02 au cutoff.

Are there recommendations on this?
Which values are more commonly used by textbooks?


texts:
Understanding "Gay-Lussac's law of Gaseous volumes/combining volumes". So I was reading Wikipedia and stumble across this. It defines it as follows "The ratio between the volumes of the reactant gases and the gaseous products can be expressed in simple whole numbers" and then give an example of
$$\ce{2H2 + O2 -> 2H2O}$$
The problem is that example does not fit the definition. The volume of reactants is $3x$ where $x$ is a variable. The volume of product is $2x$. The ratio is $\frac 3 2$, which is not a whole number. Clearly, something is wrong here or something is wrong with me. Either way, can anyone help?


texts:
Calculate the $\ce{pH}$ of a $100$ $\ce{mL}$ solution containing $0$$.0375$ moles of the weak base, Sodium Benzoate, $\ce{C6H5COONa}$.

  $$\ce{C6H5COO + H2O -> C6H6COO- + OH-}$$

$$\frac{0.0375 ~\mathrm{mol}}{.100~ \mathrm{L}} = 0.375~M$$
$$\ce{pOH} = 0.43$$
$$\ce{pH} = 13.57$$

Is this right? Thank you.


texts: Shouldn't the pressure of gas above a liquid slightly decrease when some of its molecules dissolves in the liquid?

texts:
Lets say a liquid and gas above are in equilibrium.

(1) Now if I suddenly increase the pressure of the gas it will take some time for some molecules of the gas to enter the liquid and get dissolved. When its finally done and equilibrium is reached shouldn't the pressure of the gas be a little lesser?

(2) Conversely if I violently shake a carbonated water bottle shouldn't the pressure increase a tiny little bit?

In many sources I have read that the pressure doesn't change at all when shaking. It does increase a little bit because of the energy we are giving while shaking.

What I want to know is a detailed explanation of the above two main questions.


texts: Do polycarbonate and/or polyurethane have latex?

texts:
I have a severe latex allergy which hinders my health every day via hives, inflammation, and breathing trouble. I am trying to find a cell phone that is not going to cause anaphylaxis or other reactions. Neither smartphones nor their companies are smart enough to know what their products are made of.

I know from wheelchair experience that polyurethane bothers me. I believe it has latex or a latex-like component in its make-up, but I would like to clarify this.

It appears by touch that polycarbonate is not as bad, but it just depends on the item in question...and usually I have already reacted to something else before trying to touch this.

Could you verify/explain if polycarbonate or polyurethane have latex? For that matter does polyethylene?


texts: How does the work that won the 2012 Sustainable Chemistry Award contribute to sustainable chemistry?

texts:
I'm seeking a lay explanation for how the work of Dr Marc Taillefer that won the 2012 European Sustainable Chemistry Award, contributes to sustainable chemistry.

From the press release, Dr. Taillefer

  is being recognised for his seminal contribution to the field of
  homogeneously catalysed coupling reactions leading to C—C, C—N, C—O, C—P bonds. His team at
  the Institut Charles Gerhardt, ICG (Montpellier, France) is investigating for a decade the
  environmentally sustainable conversion of small molecules into more valuable substances
  catalysed by copper and iron molecular complexes. This renaissance of “Ullmann type arylations” is now often used at the academic or industrial level and avoids the use of more expensive catalysts based on palladium.

The objectives  of the award are (to quote from this press release) to:

  Recognise individuals or small research groups which make an outstanding contribution to sustainable development by applying green and sustainable chemistry.
  Promote innovation in chemistry and chemicals that will deliver clear improvements in the sustainable production and use of chemicals and chemical products.
  Demonstrate that chemistry and chemicals can play a central role in delivering society’s needs, while minimizing and solving environmental problems.


texts: Why is 2-(3-aminomethyl-2-hydroxypropyl) cyclohexan-1-one named so and not 2-(2-hydroxy-4-aminobutyl) cyclohexan-1-one?

texts: What is wrong with naming it as 2-(2-hydroxy-4-aminobutyl) cyclohexan-1-one and taking the side chain to be having 4 carbon atoms with NH as substituent on the last? Would someone please explain this? This is the exact picture given in my book labelled 2-(3-aminomethyl-2-hydroxypropyl) cyclohexan-1-one.


texts: What are the benefits of using zero capillary voltage for discarding fractions in LC–ESI–MS/MS?

texts:
In the second episode of The Association for
Mass Spectrometry & Advances in the Clinical Lab (MSACL) podcast, namely Getting going with mass spectrometry : Josh learns chromatography (aired 2021-01-07), Dr. Russell Grant mentioned the following tip at 01:03:11 (I apologize in advance for any inaccuracies in the transcript):

The other thing that is often forgotten there is that you can drop the capillary voltage to zero. It's not as good as the diverter valve, but you are not going to be pulling the stuff towards the mass-spectrometer. If you only have a couple of windows and a bunch of junk, you can just keep capillary voltage on during these desired windows and save your diverter valves' maintenance time because they can become maintenance-limiting.

I would think it would lead to a more frequent cleaning of the ionization chamber. Is the gain in postponed maintenance of a diverter valve really worth it?
Are there any other use cases when disabling capillary voltage could be a superior alternative to using a diverter valve?


texts:
Why are acetals stable to bases and nucleophiles?

Could it be due to electronic effects? Lone pairs on the two oxygen atoms create an unfavorable environment for the approaching nucleophiles and bases. Or could it also be steric factors?


texts: What is the timescale of disulfide bond formation?

texts:
What is the timescale of disulfide bond formation in a given protein? What influences it? Finally, how does one actually measure it?

From what I understand, the reduction and oxidation of bonds happens on the order of 10-8s. However, it appears that the timescale of disulfide bond formation in macromolecules scales with the size of the macromolecule.


texts:
I've read this in a book

It says the state having three parallel spin is called triplet state .
But as far as I know it is determined by "2S+1", from this it comes out to be 4 . Then how it is "Triplet (3) " ?


texts: Why does N,N-dimethyl-1-phenylmethanamine (the left molecule in the picture) undergo hydrogenolysis of the C–N bond readily while 2-methyl-1,2,3,4-tetrahydroisoquinoline (right) doesn't react at all?


texts: Can't we reduce climate change by converting CO2 & CH4?

texts:
Straight off I want to say, I never took chemistry classes, so my understanding is very limited. My question is considering the equations below, why is it so hard to reduce greenhouse gases? Is it simply a matter of conversion requiring too much energy?

Can't we remove carbon dioxide & methane from the atmosphere by converting them into water and carbon?

$$\ce{CO2 + CH4 -> 2H2O + 2C}$$

Or by converting them into water and propane?

$$\ce{CO2 + 5CH4 -> 2H2O + 2C3H8}$$


texts:
TL;DR;
I need a compound that is harmeless to the human body, odorless, tasteless, causes some kind of visible reaction (urine coloration perhaps) AND can be bought without medical recomendation.
LONG VERSION;
Food stealing in my company fridge has become a serious problem. It's not only a recurring issue but a targeted one... our thief has been targeting "high" value, particularly coconut water. HR seems to ignore our complains... so I decided to take matters in my own hands... since I have access to timesheets, I thought that if I can scare out thief to leave work or skip it, I can narrow-it-down/point-him-out because we have about 30 people in our office...


texts: Why are conformational isomers considered as isomers?

texts:
I was taught that geometric (cis-trans) isomers are considered isomers because there is a high energy barrier to breaking the double bond for rotation (to convert into the other isomer).
 Given that there is a low energy barrier to rotation about a single bond, why are conformational isomers considered as isomers?


texts: Concentration cell lower half cell concentration from measured cell potential

texts:
I am trying to find the Ksp of silver thiocyanate:
AgSCN(s) --> Ag+ (aq)SCN-(aq)

but I need to first prove that the lower [Ag+] = 1.27-12 M, but don't know how to find it.

The data I am given:
Volume of 10-4 M Ag+ solution used: 10.00ml

Volume of 1.0 M KSCN added: 50.00ml

Measured cell potential when an Ag(s) electrode was placed into the above mixture, and then joined to the Ag+(0.1M)/Ag(s) half cell: 0.645V

Results:
Calculated lower [Ag+] from cell potential: 1.27-12 M

I am suppose to use this equation for the concentration cell:

where n is the number of electrons.

So really my question is how I would go about finding the higher concentration of Ag+ and then use that to determine that lower [Ag+] = 1.27-12M


texts: What is product obtained when B2O3 is reacted with NaOH?

texts: Will the product be a metaborate ($\ce{BO2-}$) or a borate ($\ce{BO3-}$) or anything else and why?


texts: Why do we need the rms, mean, and most probable velocities?

texts:
In the kinetic theory of gases, we have rms (root mean square), mean, and mp (most probable) velocities. I understand the concept well. But my question is why do we have three different kinds of velocities? Why don't we stick onto any one of them? What is the significance of these velocities?

And it would be helpful if someone could explain how:

$$\bar{v} = \sqrt{\frac{8RT}{\pi M}}$$


texts: What is the reason behind the formation of different shapes of crystals for different osazones? Like glucose osazone- needle shaped, maltose osazone- sunflower shaped, lactose osazone - powderpuff shaped. Does this involves hydrogen bonds only or something else? If so then can I be able to determine the crystal shape of different osazones by simple calculations?


texts: Can there be any substance whose number of electrons and protons are different at neutral state

texts: I want to ask that if there any substance that has the different number of electrons and protons at its neutral state


texts: How many types of ice exist and what is their nomenclature? I know that the ice on Earth is $I_h$, but why so?


texts: How do electrostatic effects effect facial selectivity in addition to cyclic oxo-carbeniums?

texts:
I was reviewing Dave Evans' notes for stereochemistry of C=X electrophile additions, and found this slide detailing differences in additions to cyclic oxo-carbenium electrophiles, but I don't understand why this selectivity is seen. With the OBn group, I can see that adding on the same face as the OBn is favored, compared with the methyl substituent where adding trans is favored, but I cannot figure out why.
In looking at the mechanism for allylsilane addition I can see that a positive charge builds up on the nucleophile's central carbon. Is this what is stabilized by the neighboring OBn group that effects selectivity?


texts: What is the physical state of the gas adsorbed on a solid adsorbent?

texts:
I am studying surface chemistry in high school I have this doubt and I am unable to find a answer your help is appreciated
 I searched for the answer on google I asked my chemistry teacher he said the question is beyond high school's curriculum and I even asked some of my friends but all in vain.


texts:
Any suggestions on diagramming the chemical structure for cummingtonite?
$$\ce{(Mg,Fe)_7 Si_8 O_{22} (OH)_2}$$
As I understand it, the $\ce{(Mg,Fe)_7}$ says the molecule has seven atoms that could be either Magnesium or Iron, with probably more Magnesium than Iron, meaning the structure isn't precisely defined, i.e. a mineral not a specific molecule.  Is there a suitable way to diagram this that looks nice but not excessively complex?

In fact, I'm rather ignorant about chemistry, but started screen printing subtlety goofy neck ties.  I'm envisioning doing essentially this but vertically and adding a chemical structure diagram.  I'll do the final pattern in latex if possible.

p.s.  If I were making ties professionally, maybe I'd diagram an assortment of different cummingtonite molecules as a background for the formula.  I'm not doing that, way beyond my screen printing ability.  Just curious though, how does one know the probability distribution for the Magnesium and Iron?  Just varies by sample perhaps?


texts: What's the composition of gun smoke and is it dangerous?

texts:
Background

I've been conducting an informal (i.e. mental) risk assessment of visiting gun ranges. There are a couple of obvious sources of hazard:

Injury by bullet
Hearing loss
Hot casings flying around
Gun malfunction

The first one is addressed by the fact that you should assume every gun to be loaded until personally convinced otherwise, and to always keep it pointed at the target area when handling the weapon. The second and third points are addressed by safety measures such as wearing ear and eye protective equipment.
The fourth one is kind of a wildcard, because you would assume that people who go shoot guns in a range are professionals with training. This may not always be the case, and statistics of that should be taken into account in the final verdict of the risk assessment, but I will ignore it for the time being.

The Question

Suddenly, I was struck by the idea that guns also may pose a respiratory hazard. The smoke that is formed has a distinct smell, possibly combined from the lubricant on the gun and the combusted propellant of the bullet. What exactly is this "gun smoke" made of, and should I be concerned for my health in this regard?

An image to show what this gun smoke can look like (Source: Arizona Sonora News):

Bonus Question

There is an additional level of concern when handling even larger payloads than a simple 9 mm bullet, but the documentation may be restricted and as such I do not require an answer to the following question: Are there any requirements for military personnel operating cannons and other large artillery to protect their airways from the fumes?


texts:
I'm trying to convert $\ce{CO2}$ ppm (volume) in the air into ppm (weight) in the water.

I found this formula

  $\mathrm{mg \ m^{-3}}$ = (ppmv)(MW) / [($0.08205$) (¦$\mathrm{K}$)]

where,

ppmv = air pollutant concentration, in parts per million by volume

$\mathrm{mg \ m^{-3}}$ = milligrams of pollutant per cubic meter of air

$\mathrm{K}$ = atmospheric temperature in degrees Kelvin = $273.15$ + $^\circ C$

$0.08205$ = universal gas law constant in $\mathrm{L\ atm \ mol^{-1} K^{-1}}$

MW = molecular weight of the air pollutant (dimensionless)

$\mathrm{atm}$ = absolute atmosperic pressure in atmospheres

$\mathrm{g \ mol}$ = gram mole

I've read the $\mathrm{mg \ m^{-3}}$ is a subunit of ppmw, so is it correct to say $\mathrm{mg \ m^{-3}}$ is ppmw?


texts: What is the relation between ionization energy and electropositivity?

texts: Electropositivity of an element is defined as a measure of element's ability to donate electrons while Ionization energy or Ionization potential is defined as the energy required to dispel a loosely held electron from the valence shell. These two terms sound closely related to me or they are just measure and energy?


texts: How do I calculate the cost of a single Aluminum atom?

texts:
I am doing a Chemistry assignment in which I was given a piece of aluminum foil which I had to measure and use for my calculations. I am supposed to calculate the cost of a single aluminum atom using the given data from my teacher and the data which I have measured from my piece of aluminum foil. I understand the basic concept of how I am supposed to do this, but I am having some trouble. Here is the data:

Data given by teacher:
  Cost of a roll           $5.53
  Roll size                30.5 cm x 30.5 m
  Density of Al            2.70 g/cm^3
  Molar Mass Al            26.98 g/mol

Data measured from my piece of Aluminum foil:
  Mass     1.35 g
  Size     18.6 cm x 12.5 cm

I have determined a way to do this, but I am having trouble with it. First of all, I have determined the amount in moles which is $\mathrm{0.0500~mol}$. Then I multiplied the amount in moles with Avogadro's constant ($\mathrm{6.02 \cdot 10^{23}~mol^{-1}}$) to determine the number of aluminum atoms in the piece of aluminum foil I received which is $\mathrm{3.01 \cdot 10^{22}}~\text{atoms}$. Now I just have to find the cost of a single aluminum atom, but this is where I am stuck. I cannot use the cost of the aluminum foil roll to divide it by the number of atoms since I was given a piece of aluminum foil so I need to find the cost of the piece of aluminum foil and then divide it by the number of atoms.

So basically my question is: How do I find the cost of the piece of aluminum foil? If I can find the cost then I can divide it by the number of atoms to determine the cost of a single aluminum atom.

However, if there is a way to find the number of atoms in the roll of aluminum foil, I could then use the cost of the aluminum roll to find the cost of a single aluminum atom. Please explain if there is a way to do this using the data given by the teacher.


texts: What's the difference between graphite, nanotubes, and fullerenes?

texts: I understand that all of these are made up of carbon atoms but I don't understand what differentiates them. Since they are carbon they all must have covalent bonds, right?


texts: What is the condensed formula for cyclohexane?

texts:
I can't find it written anywhere and my guess is that it doesn't exist as it would be impossible to write it out in a straight line.
Could $\ce{CH2CH2CH2CH2CH2CH2}$ be used ?


texts: Do bond lengths vary across molecules of the same kind?

texts:
I only have superficial knowledge of chemistry, and today I found out about bond length for the first time. For example, on Wikipedia it says that all C-C bonds of benzene have a length of 140 picometres (both C-C and C=C, I think). But is this exactly true for all benzene molecules?

Or does bond length of C-C vary slightly for 10 molecules of benzene? Is 140pm an average distance for a million molecules, or each and every benzene molecule has bonds of length 140pm? Is this a fundamental and unvarying length of the benzene molecule, so that a different length cannot possibly occur?

I know that during studies of the bond length in the laboratory, each individual measurement has a slight error. I'm not asking about that.


texts: The amount of the DMF in the Sonogashira coupling - why it is of importance?

texts:
I was looking for some protocols for Sonogashira coupling and have found that in many papers the amount of the DMF used is exactly 2 ml per mole of the substrate.

Is there any reason for that? Usually, for other reactions, we can see, that articles report more-less random amount of solvents, like 10, 50, 100 ml - some "simple" numbers. But in this case I see numbers like 68 ml (why not 70?). Why must it be exactly 2 ml/mole?

some refs:

http://pubs.acs.org/doi/suppl/10.1021/ol049474j/suppl_file/ol049474jsi20040410_035107.pdf

http://www.sciencedirect.com/science/article/pii/S0040402000008772

http://pubs.acs.org/doi/suppl/10.1021/jo8020264/suppl_file/jo8020264_si_001.pdf


texts: Which will be the major monochlorination product?

texts:
Which of these compounds represents the major monochlorination isomer formed in the following reaction?

According to selectivity theory, the answer should be (c). However, the given answer is (b).


texts: Thermal conductivity and enthalphy data for nitrogen gas

texts: I am struggling to find the data for thermal conductivity and ethalphy of nitrogen gas at reduced pressure (500 mbar). Most of the information is for nitrogen gas at 1 bar or above. Does anyone know where I can find this information? Specifically, I need to know the thermal conductivity and enthalphy of nitrogen at 295.15 K (22 degrees) and pressure of 0.5 bar (500mbar)


texts: I have been researching on E227 (Calcium Bisulfite), and could find minimal information about how it acts as a preservative and how effective it is. I could only find that it preserves by converting itself to sulfurous acid in an acidic liquid, but could not find out how effective and how exactly it preserves. I would appreciate any help.


texts: Variation within a chromatography with the same sample

texts:
What are some possible explanations to why the exact same sample in SEC HPLC differ in their peak heights, although it's the same chromatographic profile?

The sample contains cell culture medium (undiluted) into a 10mM phosphate NaCl buffer. Is it possible that the sample is overloaded, might this be the cause for such different results?

After each sample there's a 1x column bed volume (24ml) wash with the phosphate buffer.

Any theories based on experience or otherwise?

Edit:

Sample 1:

Peak 1: 166292μV,

Peak 2: 199835μV,

Peak 3: 168024μV,

Peak 4: 78483μV

Sample 2:

Peak 1: 96936μV,

Peak 2: 142119μV,

Peak 3: 148060μV,

Peak 4: 195584μV

Sample 3:

Peak 1: 56769μV,

Peak 2: 88114μV,

Peak 3: 82351μV,

Peak 4: 176517μV

Chromatogam looks something like this (Peak count from left to right)


texts: Difference in leaving group ability due to variation in nucleophiles

texts:
Wikipedia writes:

  There can still exist contextual differences in leaving group ability in the purest form, that is when the actual group that leaves is not affected by the reaction conditions (by protonation or Lewis acid complexation) and the departure of the leaving group occurs in the rate determining step. In the situation where other variables are held constant (nature of the alkyl electrophile, solvent, etc.), a change in nucleophile can lead to a change in the order of reactivity for leaving groups. In the case below, tosylate is the best leaving group when ethoxide is the nucleophile, but iodide and even bromide become better leaving groups in the case of the thiolate nucleophile.

Why is it so?As far as I know, leaving group ability is basically how stabilized the leaving group is when it exists as an independent species. I can't see why it depends on the nucleophile


texts: Which potentials are suitable for molecular dynamics simulation of simple explicit solvents?

texts: Which potentials (force fields) are suitable for adequately simulating (mixtures of) explicit solvents? Interesting rheological properties include viscosity, surface tension, heat capacity.


texts: Improvement of the thermal stability of hydrous zirconia by post-synthesis treatment with NaOH and NH4OH solutions

texts:
I read a paper about how researchers improved the thermal stability of hydrous zirconia by post-synthesis treatment with $\ce{NaOH}$ and $\ce{NH4OH}$.[1]

While the surface area of non-treated zirconia though more, but after calcinations at high temperatures the % decrease of the treated zirconias was very less as compared to non treated zirconia.
Is there any reason for this observation besides the changes the changes in pore volume and size?
Any specific reason for the morphology obtained?

G. Aguila, S. Guerrero, F. Gracia, P. Araya, Appl. Cat. A: General 2006, 305 (2), 219-232. DOI: 10.1016/j.apcata.2006.03.025


texts: How to calculate the magnitude of magnetic field of an orbital?

texts:
I read that according to QM  the electron in the ground state orbital produces no magnetic field, if that is true, can you explain why so and in what states there is a magnetic field and how that is produced? Why the difference?

Anyway, I am interested in learning how the classical model calculated it, since I read different values in different papers: for example hyperphysics says its value is .4 T, elesewhere I found .5 and .6, and If I use the classical formula I get .125 T

Does 0.4 Tesla refers to the exact value of the magnitude of the magnetic field od 1S state?


texts: What will be the product of Wolff–Kishner reduction in presence of hydrogen peroxide?

texts:
My textbook exercise gives this reaction.
What I observe is only the alkene part at the bottom changes to alkane.
I know the procedure of ordinary Wolff–Kishner reaction (shown in img given below), but peroxide makes it difficult.
1 and 2 represents the catalyst addition order.
Please explain why this happens?
Does this reaction remove double bonds?


texts: Overall effective activation energy for parallel reactions

texts:
Today, I was solving a question from Chemical Kinetics.

Consider the following parallel, first order reactions:

$$\begin{align}
\ce{A -> P} \tag{1} \\
\ce{A -> Q} \tag{2}
\end{align}$$

with rate constants $k_1$ and $k_2$, and activation energies $E_1$ and $E_2$ respectively.

I was asked to calculate the overall activation energy $(E)$ for the decay of A.

In my book a formula for $E$ is given to be :

$$E = \frac{E_1k_1+E_2k_2}{k_1+k_2}$$

This formula works well and provides correct answer, but I was trying to derive this expression using the Arrhenius equation. But I didn't succeed. I could deduce that,

Since:

$$ k_1=A_1 \mathrm e^{-E_1/RT}~; ~ k_2=A_2 \mathrm e^{-E_2/RT}$$

and

$$k_{\text{eff.}}= k_1+k_2 = A_{\text{eff.}}\mathrm e^{-E/RT}; $$

Using these both:

$$k_1+k_2= A_1 \mathrm e^{-E_1/RT} + A_2 \mathrm e^{-E_2/RT}$$

Now, I have no clue what to do.


texts: Post-synthetic Anisotropic Wet-Chemical Etching of Colloidal Sodalite ZIF Crystals

texts:
It's well known that Metal-organic Frameworks can be made by attaching inorganic metal ions to organic linkers via strong chemical bonds, ZIF-67 is one of this big family which could be prepared by using Cobalt source with some kind of organic linkers.
my question is how could we control the structure of ZIF-67 by using wet chemical etching in order to break the links and in particular get sheet like structure?


texts:
I seek to put a layer of fluorine on a rotationally molded cross-linked polyethylene (XPE) plastic gasoline tank. I sell tanks and they will be more eco-friendly if I can accomplish this.

I am an electrical engineer and my last experience with chemistry was Chem 200 lecture and lab at SDSU, a one semester intensive "all of chemistry for engineers" kind of course. I asked a chemistry professor at my alma mater about this, who said:

  Xenon difluoride is a powerful fluorinating agent, and is soluble
  (according to Wikipedia) in anhydrous methyl cyanide and several
  fluorinated solvents.  Offhand, this looks to me like it would do the
  job, but it's not a friendly compound (toxic, possibly corrosive).

The concept is already in place all around us: any time you buy a plastic jug with harsh chemicals in it, the jug has been fluorinated. So far, the majority of my learning is confirmation that yes, indeed, fluorinating polyethylene (PE) surfaces with $\ce{XeF2}$ leads to decreased gas permeability.

I've done a bit of Googling and bought a couple of great textbooks, Fluoropolymers 1; Synthesis and Fluoropolymers 2; Properties. Fluoropolymers 1 seems to have great stuff in a couple sections. Perusing Fluoropolymers 2, I haven't seen anything jump out at me yet.

There are two methods I have read about:

Involves an oven, steady high temperature, and plasma discharge.
"Surface Fluorination of Polymers Using Xenon Difluoride", or Gaseous $\ce{XeF2}$ and PE are placed in a "stainless steel reactor" and left alone.

Seeing the options, the 2nd seems the way to go, and this seems to be the epic equation concerning my quest quoted from Fluoropolymers 1 page 231, section 15.3:

  The comparative accessibility and desirable properties of $\ce{XeF2}$ enable
  its use for the synthesis of fluoroorganic compounds under “mild”
  conditions. As a fluorinating agent $\ce{XeF2}$ can be used to effect
  electrophilic fluorination of various organic compounds with good
  yield and it is a useful reagent for generating radical cations.
  ... In many cases XeF2 is an attractive alternative to the
  conventional Balz–Schiemann reaction for the preparation of
  fluorinated aromatic compounds, e.g., fluorobenzenes:

  $\ce{RC6H6 ->C[XeF2] Rc6H5F + Xe + HF ->C[XeF2] RC6H4F2 }$

  Xenon difluoride reacts with carbon–carbon single, double, and triple bonds
  giving addition fluoroorganic compounds, e.g.,

  $\ce{R-CH=CH2 ->C[XeF2] RCH2-CHF2 + Xe}$

  and

  $\ce{RCH2-CH3 ->C[XeF2] RCHF-CH3 + Xe + HF ->C[XeF2] RCF2-CH3 + Xe + HF}$

And this quote from page 236 gives me great hope:

  Another argument in favor of the $\ce{XeF2}$ method is the evidence that since 1995 it
  has been used by a manufacturing company that had no previous experience with
  direct fluorination or fluorine at all.

... for I'm in the same position now!

How do I actually perform a fluorination surface treatment my XPE products?

Where / how do I go about getting $\ce{XeF2}$? And if it is soluble in a "fluorinated solvent" like my prof said, is there a way I can flush this through the interior of my tanks in a controlled manner that would accomplish some degree of fluorination?

Edited to add 10-22-12: I called a few companies today. Everyone is pointing me to pay Fluoro-Seal to do this. They are the only company providing this service in the US. I'll need to ship my products to them, wait a couple weeks, and pay $15~45 each tank. I'd still like some kind of bath or wash to do this. This is why no-one making replacement tanks has them emissions legal... all this triples my cost.

Edited to add 12-30-13: Fluoro-Seal has given up on fluorinating rotationally molded PE. I'm pushing a plastics manufacturer to develop their existing acetel product to work with rotational molding. Their solution for injection and blow molding is in production and impervious to fuels (they have parts in nearly all automotive fuel systems in the US right now). So there's hope for a solution; however it seems impossible to fluorinate PE.


texts: Directing effect in Intramolecular Friedel Crafts Alkylation

texts:
This reaction should cause ring closure at either the $o-$ or $p-$ position relative to the methyl substituent on the ring (as methyl is an $o,p-$directing group), giving the following products:

The question is: Which one of these is the major product? Is substitution preferred at the ortho position or para position, and why?

A few more examples of these types of questions:

This would give which of the following?


texts: What is meant by "rotation about an axis that passes through a lattice point"?

texts:
I am currently studying Introduction to Solid State Physics, 8th edition, by Charles Kittel. In the section Fundamental Types of Lattices of chapter 1, the author says the following:

Crystal lattices can be carried or mapped into themselves by the lattice translations $\mathbf{T}$ and by various other symmetry operations. A typical symmetry operation is that of rotation about an axis that passes through a lattice point.

It's unclear to me what is meant by "rotation about an axis that passes through a lattice point". In doing research, I found this page, but I'm not completely sure that this is referring to the same phenomenon. I would greatly appreciate it if people would please take the time to clarify this. I would especially appreciate pictures depicting this, as well as the mathematics itself.


texts: Is there an easy way to find number of valence electrons"

texts:
I want an high-school level answer. What I mean with "valence electrons" is the outermost electrons in that atoms' electronic arrangement? For example, 3 in an atom with an electronic arrangement of 2, 8, 3.)

Without actually writing the electron configuration, or orbitals, and knowing electron number, is there any way to find this number easily?

Also, is there an easy way to find if certain atom fits "atomic/orbital symmetry" given the numbers of electrons? (I don't know the english words for this and couldn't find them. So I translated it literally, but what I mean is, if orbital is half-full or full i.e  $\mathrm{s^1}$ or $\mathrm{2p^3}$ or $\mathrm{2p^6}$ and so on... hope you understand what I am trying to say)

I am asking this because sometimes questions give me electron numbers in a range of 40+ and just writing it out doesn't seem like a good way.


texts: Why doesnt the overall rate of a reaction increase if you increase the concentration of a reactant in a non rate determining step?

texts: We say that the overall rate doesnt increase if we increase the concentration of a reactant in a non rate determining step. Does that mean that the speed of that non rate determining step increase but at the same time something happens to counter the increase in speed? Because it doesnt make sense to say that the speed doesnt increase with increase in concentration.


texts: Are there colorful metals besides gold and copper?

texts: Are there yellow metals besides gold? Are there metals with color different than yellow and grey/silver or reddish?


texts:
I am trying to plotting the angular parts of a wavefunction ($Y_{(m,l)}(\theta, \phi)$) with Wolfram Mathematica. this is the table of spherical harmonics.

I think the shape of these function should looks round each part of p and d orbitals is a ellipsoid looks like an egg, like this figure:

I have 2 question with my result:

1. All my figure of p orbitals only have half part the orbital above(examples:
$p_0$ orbital and $p_y$ orbital). And all the d orbitals looks longer than that above (example: $d_{xz}$).

2. When I square the spherical haromics ($[Y_{(m,l)}(\theta, \phi)]^2$), The p orbitals looks the same as the top figure (example: $(p_y)^2$) ,but the p orbitals getting far longer and thinner than that before squared, also the figure in the top (example:$(d_{xz})^2$)

What's wrong with my plot or the shape is not looks like eggs? Do I miss something that make the figure only have half part?


texts:
What is the order of stability of the following carbocations?

I think that it is clear thatt the first two are more stable than the last 2 as they involve resonance in ring, i.e. the mesomeric effect. Also as the first one has a bigger carbon group attached to it so it will show a larger inductive effect, therefore $1>2$. The third one has a tertiary carbon which is stabilized by hyperconjugation, while the fourthth shows resonance.
As resonance is given more priority the fourth should be more stable, but this doesn't match with the answer.


texts: How does water deionization process work?

texts: What are the technical/scientific details behind the process of water deionization? How does deionization machines like those manufactured by Millipore work?


texts:
I became quite confused about Jacobi coordinates. Until now I've been used to them as the coordinate system, where coordinates are vectors pointing to the center of mass of previous "subsystem", as we can see in the picture

Also, they're described in the same way in the Wikipedia.

But today I've met two colleagues, who were talking about Jacobi coordinates in 3-atomic system as about "vector-vector-angle", looking like this

with descriptor set being $\left(R,r,\cos^2(\Theta)\right)$.

Is this coordinate system also called Jacobi coordinates? And if it isn't, what's its real name?


texts: Why are chemistry droppers bad at holding bromine?

texts: Question in my chemistry test last week. The question was related to a previous question on bromine's density.


texts: Balancing the equation when MnO₂ is reduced to MnO by H₂(g)

texts:
I am studying for a final tomorrow and I was going through some problems on older exams and came across one which I wasn't really sure how to solve.

The problem is to write the balance equation when:

managnese(IV)oxide is reduced to manganese(II) oxide by hydrogen gas.

I took a few approaches to this, because at first I did not realize it say reduced "by" hydrogen gas. This part threw me off because I initially added $\ce{H2(g)}$ to the product side.

So far I have:
$\ce{MnO2(s) + H2(g)-> MnO(s) + H2O(l)}$ which is not balanced yet. I noticed in this case the conventional type of balancing the equation does not work. Would this be a redox rxn in which I find each half reaction and then balance?

I am completely stuck at this point, and I don't think my formula is correct. Does anyone have any insight or good examples ?


texts: In this reaction I am unable to understand its mechanism. How the peroxide HCCL3 is causing the ring contraction. I know that the 8 member ring is unstable due to strain and hence it will try to contract. But I am not able to initiate the mechanism due to reagents present. Please can someone explain me how the contraction of 8 members ring to 2 five member ring is taking place?


texts: Why is antimony pentafluoride a stronger Lewis acid than phosphorus pentafluoride or arsenic pentafluoride?

texts:
How can these relative reactivities as a Lewis acids be rationalized:

$$\ce{SbF5 > AsF5 > PF5}$$

One simple argument could be the size of the $\ce{Sb}$-center: Because it is bigger than for example a $\ce{P}$-center it can accept more ligands.
I couldn't find a more precise explanation or rationalisation. My knowledge of the MO diagram of hypercoordinative compounds is really basic, so maybe this could provide - energy differences of the LUMO's of the several compounds - a neat access?


texts:
I have been told to answer the following question:

  Seven different compounds, all either alcohols or ethers,
  contained 21.62% oxygen. Find the structural formula for all of these compounds and name the alcohols.

So far I've tried using empirical formula calculations to work out a simple formula but this has yielded no results because I do not know the exact ratio of hydrogen to carbon in the formula nor do I know any masses which I could use to scale up the empirical formula into a molecular formula. It seems to me that there just isn't enough information to answer the question - after hours of searching I can't even find one, let alone seven. I'm sure the answer is stupidly easy but it's evaded me. Does anyone have any suggestions of things I might be able to try? This question is UK A-Level standard.


texts: Calculating partial pressures from mixture of gases

texts:
A gas is enclosed in a container at $35~\mathrm{m^3\,mol^{-1}}$ and has the following composition at $49\,\mathrm{^\circ C}$
$\ce{N_2} \ 2\,\% $
$\ce{CH_4} \ 79 \,\%$
$\ce{C_2H_6} \ 19 \,\%$
Assuming an ideal gas, calculate the partial pressure of each component (in kPa).

My working so far:
I chose $100 \,\mathrm{mol}$ because I've been given percentages and it's a nice number to work with, and I multiplied this with $35 \,\mathrm{m^3\, mol^{-1}}$ to get $3500 \,\mathrm{m^3}$
I used $P=\frac{nRT}{V}$ to calculate an overall pressure but got $76\, \mathrm{Pa}$ which seems way too low. Have I done anything wrong?


texts: Which electrons are in HOMO in a peptide bond?

texts: We've recently studied the absorption of UV light by polypeptides, and found that the peptide bonds itself absorhs UV light at around 210nm. I'm confused about what feature causes this to happen.


texts: Why is the ROHF spin density of the propenyl radical not symmetric?

texts:
I was preparing some material for my students and in order to illustrate the concept of spin density and how the ROHF method gives a purer description of this property than the UHF method. I prepared a simple calculation for the $\ce{CH3}$ and $\ce{CH2CHCH2}$ radicals.

The calculations for both radicals performed properly. Given the symmetry of the molecules, I expected the distributions to be symmetric. That expectation was borne by the results of the calculations for the methyl radical and the UHF method of the allyl radical. However, in the case of the allyl radical the spin density surface is asymmetric as shown in the following picture obtained with GaussView 5.

The canonical MO have the proper symmetry (see below)

Can anybody point to an explanation of these behaviour or a mistake in the calculation?

P.D. Find enclose a copy of the Gaussian input field I used in the calculation.

%chk=c3h5_rohf.chk
# opt=tight rohf/6-31++g(d,p) guess=mix

ROHF

0 2
 C
 H                  1    1.06999999
 C                  1    rCC    2  ACCH
 H                  3    rCH    1  AHCC    2    0.0
 H                  3    rCH    1  AHCC    2  180.0
 C                  1    rCC    2  ACCH    3  180.0
 H                  6    rCH    1  AHCC    3  180.0
 H                  6    rCH    1  AHCC    3    0.0

 rCC 1.40140000
 rCH 1.0700000
 ACCH 120.0
 AHCC 120.0


texts:
My question is: Is hydrogen-rich water true? I am aware of the alkaline water. I have read several articles in the Internet regarding this kind of water but I cannot seem to be convinced. Wikipedia isn't even talking about it.

I am puzzled with how can a water be enriched with hydrogen. It's definitely $\ce{H2O}$ and everybody knows it. It's not water anymore if it's not $\ce{H2O}$.

This link is one of the examples of websites that I read about hydrogen-rich water.


texts: Why does allosteric binding produce a sigmoidal curve?

texts:
Allosteric binding is where the enzyme can be regulated through having ligands bind onto somewhere that is not the active site. This will then induce a conformational change on the active site, hence preventing binding and catalysis.
Often after a long pathway, the final product can act as the modulator and bind at the allosteric site of the first enzyme.
My question is why does the curve now change to look sigmoidal instead of hyperbolic?

I get that allosteric binding should affect the shape - but this is not what I expected. What I do not understand is why does the velocity decrease so sharply at low concentrations of substrate?
Allosteric binding should mean that at small amounts of substrate, there should be very little amounts of reaction. Thus, there are small amounts of product and hence very little allosteric binding. Thus the reaction should go at full speed, looking just like the diagram on the left. It is only at higher concentrations of substrate that the modulating effect would kick in.
Where is my reasoning wrong?


texts: Can gamma radiation cause transmutation?

texts: In irradiation of food for sterilisation, is gamma radiation absorbed by the food? If so, can it theoretically cause production of radioisotopes? Or does it ionise atoms in the food?


texts: Acidity/basicity of oxides across the periodic table

texts: Recently while self-studying my chemistry book, it dawned on me that metals form basic oxides and nonmetals forma acidic oxides. Why is this?


texts: What's the reason for the instability of ethylene dione?

texts:
Ethylene dione, with a chemical formula $\ce{C2O2}$ and an IUPAC name of ethene-1,2-dione, is an oxocarbon.

The Wikipedia page says:

  The existence of $\ce{OCCO}$ was first suggested in 1913. However, despite its deceptively "simple" structure, for over a century the compound had eluded all attempts to synthesize and observe it. Such elusive nature had earned $\ce{OCCO}$ the reputation of a hypothetical compound and a mysterious, "exceedingly coy molecule".

I cannot understand what the rest of the article is telling me. So, why is ethylene dione unstable?


texts: How to extract pure caffeine from tablets?

texts:
I have some caffeine tablets and I want to extract the pure caffeine from the rest of the ingredients (caffeine 200 mg. Inactive ingredients in order are corn starch, dextrose, dicalcium phosphate, D&C yellow #10 aluminum lake, magnesium stearate, microcrystalline cellulose, silica gel).

I assume the result would be aqueous solution but any method which works would be great.


texts:
For $\pu{550.0 mL}$ of a buffer solution that is $\pu{0.170 M}$ in $\ce{CH3CH2NH2}$ and $\pu{0.150 M}$  in $\ce{CH3CH2NH3Cl}$, calculate the initial pH and the final pH after adding $\pu{0.020 mol}$ of $\ce{HCl}$.

The following is my attempt on solving this problem:

Since Kb for ethylalamine = $5.6 \times 10^{-4}$.

pKb = $-\log( 5.6 \times 10^{-4}) = 3.25$

pOH = $3.25 + \log (0.150/0.170)$

pOH = $3.196$

pH = $14 - 3.196 = 10.80$ for Initial

Final pH:

$\pu{0.170 M} * \pu{0.55 L}= 0.0935 mol$                $\ce{CH3CH2NH2}$

$\pu{0.150 M} * \pu{0.55 L} = \pu{0.0825 mol} \ce{CH3CH2NH3Cl}$,

$0.0825 - 0.02 = \pu{0.0625 mol} \ce{CH3CH2NH3Cl}$,

$0.0935 + 0.02 = \pu{0.1135 mol} \ce{CH3CH2NH2}$

pOH = $3.25 + \log(0.0625/0.1135)$

pOH = $2.991$

pH = $14 - 2.991 = 11.01$ for final

However, these values turn out to be wrong. Please help, thank you!


texts: Overall equilibrium expression for competitive equilibria

texts:
I have a case where I have two reactions that depend on a common reactant. The reactions can be written as:

I) $\ce{A + B <=> AB}$

II) $\ce{A + C <=> AC}$

We can thus write equilibrium expressions for both reactions:

I) $K_\mathrm{I} = \frac{[\ce{AB}]}{[\ce{A}][\ce{B}]}$

II) $K_\mathrm{II} = \frac{[\ce{AC}]}{[\ce{A}][\ce{C}]}$

How can I combine these equations to get an equation that relates the equilibrium concentration of B to that of C?

Secondarily, can this be extended to give an equation that relates the equilibrium concentrations of B and C to the initial concentrations of A, B and C?

I already know the equilibrium and rate constants for both reactions in isolation. If it is relevant, A is a solid with a fixed number of surface sites, to which B and  are adsorbed. B and C are in aqueous solution.


texts:
From what I understand, to get clear peaks, $\ce{Pt}$ is analyzed at $\ce{Pt}$ 4f; and $\ce{Ru}$ at $\ce{Pt}$ 3d.
However, if i'm not mistaken, charge correction is needed.
But $\ce{Ru}$ 3d(280/284 eV) overlaps with $\ce{C}$ 1s(284 eV), therefore I cannot use $\ce{C}$ 1s for charge correction. Hence, I mix in some $\ce{Au}$ powder and use $\ce{Au}$ 4f(84 eV) for charge correction and then analyze $\ce{Ru}$ at $\ce{Ru}$ 3p(461eV).
But now, $\ce{Au}$ 5p(74 eV) overlaps with $\ce{Au}$ 4f(74 eV) so I cannot analyze at $\ce{Pt}$ 4f
and I try to analyze at $\ce{Pt}$ 4p(519 eV).
However, my problem is that I'm not getting clear enough peaks. The obvious thing I can think to do is increase the number of scans or lengthen the dwell time.
But I was wondering if there are other solutions other people usually do that I might be missing.
I do see some papers that try to deconvolute $\ce{Pt}$ and $\ce{C}$ in the same region, but my professor says that this is an incorrect method because it is impossible to consider the correct charge correction that way.
Does anyone have any suggestion on how I should proceed?


texts: Nuclear reactions involve naked nuclei only. True or false?

texts: In nuclear reactions are all the species involved, naked nuclei that is, are they all atoms that have been completely stripped of their electrons? If not, then shouldn't an alpha decay result in the formation of an anion and shouldn't a beta decay result in a cation?


texts: Why does aluminum in zeolites form tetrahedras?

texts: It forms a bond with four oxygen atoms even though it has only there electrons in his outter shell?


texts: How are second and third electron affinities of atoms measured?

texts:
Wikipedia data page on electron affinities shows second and third electron affinities. Of course, they are negative, because one tries to attach electron to anion. But how are they measured or calculated in practice?

Electron affinity in Wikipedia


texts: Can aldehydes be reduced to alcohols efficiently using LiAlH4 (excluding cost effectiveness)?

texts: In my textbook (NCERT 12th class Chemistry, Part 2, India), $\ce{H2}$ with $\ce{Pd}$ catalyst is the only method mentioned.


texts: When writing the net ionic equation, if one of the products ionizes, what is the most appropriate way to account for this in the answer?

texts:
Take these two practice problems and their solutions from Ebbing (8th ed) that involve completing the molecular equation, then writing the net ionic equation:
4.42a: $\ce{Ca(OH)2(aq) + 2H2SO4(aq) -> }$
soln:
$$\ce{Ca(OH)2(aq) + 2H2SO4(aq) -> 2H2O(l) + Ca(HSO4)2(aq)}$$
$$\ce{OH-(aq) +2H+(aq) +SO4^{2-}(aq) -> H2O(l) + HSO4-(aq)\\ \text{ (ionizes to } H+ + SO4^{2-})}$$
4.42c: $\ce{NaOH(aq) + H2SO4(aq) -> }$
soln:
$$\ce{NaOH(aq) + H2SO4(aq) -> NaHSO4(aq) + H2O(l)}$$
$$\ce{OH-(aq) + H+(aq) -> H2O(l)}$$
In 4.42a the authors do not ionize the product, only note to the side that it does ionize. In 4.42c the authors do ionize the product and account for this in the net ionic equation.
In general, is one practice preferable or more correct than the other?

Please note that I did not intend to answer my own question. After reading some of the answers, I feel it is necessary to provide clarification for future readers. Hopefully, my answer is enlightening.
Let us begin with a point of interest, reading again from Ebbing:

Phosphoric acid is an example of a triprotic acid. By reacting this
acid with different amounts of a base, you can obtain a series of
salts:
$$\ce{H_3PO4(aq) + NaOH(aq) \rightarrow NaH_2PO_4(aq) + H_2O(l)}$$
$$\ce{H_3PO4(aq) + 2NaOH(aq) \rightarrow Na_2HPO_4(aq) + 2H_2O(l)}$$
$$\ce{H_3PO4(aq) + 3NaOH(aq) \rightarrow Na_3PO_4(aq) + 3H_2O(l)}$$

And now, let's consider the problem.

Problem 4.42 Complete the right side of each of the following
molecular equations. Then write the net ionic equations. Assume all
salts formed are soluble. Acid salts are possible.
a. $\ce{2H_2SO_4(aq) + Ca(OH)_2(aq) \rightarrow} $

To give us insight into the nature of this reaction, let us first consider a complete neutralization reaction for calcium hydroxide and sulfuric acid and see what that looks like.
$$\ce{1H_2SO_4(aq) + 1Ca(OH)_2(aq) \rightarrow CaSO_4(s) +2H_2O(l)}$$
Now, let us again consider our original problem in terms of the complete neutralization. We divide the coefficients by two.
$$\ce{1H_2SO_4(aq) + \frac{1}{2}Ca(OH)_2(aq) \rightarrow \text{ incomplete neutralization}} $$
This helps give us an idea of how to predict the products for the molar ratio provided. We know the acid salt formed is soluble as we are told this in the problem statement.
$$\ce{2H_2SO_4(aq) + Ca(OH)_2(aq) \rightarrow Ca(HSO_4)_2(aq) + 2H_2O(l)}$$
For the net ionic equation, we consider that $H_2SO_4$ is a strong acid and will ionize completely in solution and $Ca(OH)_2$ is a strong base and will dissociate in solution to be present entirely as ions.
$$\ce{4H^+(aq) + 2SO_4^{2-}(aq) +} Ca^{2+}(aq) \ce{+ 2OH^-(aq)} \rightarrow  Ca^{2+}(aq) \ce{+2HSO_4^-(aq) + 2H_2O(l)}$$
Eliminate the spectator ions.
$$\ce{4H^+(aq) + 2SO_4^{2-}(aq) + 2OH^-(aq) \rightarrow 2HSO_4^-(aq) + 2H_2O(l)}$$
Reduce coefficients.
$$\ce{2H^+(aq) + SO_4^{2-}(aq) + OH^-(aq) \rightarrow HSO_4^-(aq) +  H_2O(l)}$$
Note that $\ce{HSO_4^-}$ ionizes to $\ce{H^+}$ and $\ce{SO_4^{2-}}$. Substitute and reduce.
$$\ce{H^+(aq) + OH^-(aq) \rightarrow H_2O(l)}$$
We accept either form of the answer, though if to go with the former you must notate the species that ionizes, otherwise is incorrect.
$$\ce{2H^+(aq) + SO_4^{2-}(aq) + OH^-(aq) \rightarrow H_2O(l) +  HSO_4^-(aq) \text{ (ionizes to } H^+ \text{ and } SO_4^{2-}\text{)}}$$


texts: What was the lithium concentration in 1940's 7-Up?

texts:
I just came across this article in the New York Times, where lithium (or more correctly, lithium salts), a known anti-depressant had been added to beverages in the 1940's. They also mention that a study found negative correlation between the suicide rate of a county and the amount of lithium in its tap water, despite the fact that the concentration is relatively low ($\pu{<0.170 mg L^-1}$), especially compared to the doses administered in therapy.

Now I was wondering what the lithium content in those beverages was (obviously, they are not sold anymore), but couldn't find anything?

The article mentions that you can still buy lithia water ($\pu{0.50 mg L^-1}$), but I'm more interested in the 1940's 7-Up mentioned, as those probably had different food standards at the time they were made.


texts: HCl + fingernail (set for a year) + H2O2 + Cu

texts:
I had a $\ce{HCl}$ in a container which a year ago a fingernail fell into it there were no way for me to remove it. The result of $\ce{HCl}$ and that fingernail is some brownish solution as shown:

Now I have to use that $\ce{HCl}$ acid with $\ce{H2O2}$ to etch copper boards (PCB), but after a while what I get is this blueish liquid instead of the green one:

also a blue crystals forms preventing the etchant of copper:

what is that blue liquid and how can I fix this to get the $\ce{CuCl2}$ etchant?

Edit:
another image of the crystals formed on the copper:


texts: How to clean pocket pH meter before storage?

texts:
Hello.

I read about different methods how to clean this specific(attached photo)pocket pH meter before storage and i can't figure out what is the right way.

One method says to stir the pH meter(glass electrode)in distilled water and
replace the protective cap,other says to stir the glass electrode only in tap water before replace the protective cap.One says also to wipe dry with cloth(or filter paper)the measuring electrode,while other says to add few drops of storage fluid in the protective cap before replace the protective cap.Those too many methods for the same type of pH meter made me confused.What should be the right way?


texts:
Why can't you prepare Boron Trifluoride by reacting B2O3 with Carbon and Fluorine?

B2O3 + 3C + X2 ---> 2BX3 + 3CO

Why won't this work with Fluorine?

(This is not a duplicate, as the question being referred to is merely a method to synthesize Boron Triflouride. This question was concerned with why it can't be created using the given process.)


texts: What are Degenerate Rotational Energy Levels Physically?

texts:
I'm in introductory chem, so I don't have much of the physical background to really understand what's going on yet, but we're learning about rotational energy levels, and how some rotational energy levels for molecules are degenerate.

As I understand it, degenerate energy levels correspond to different "ways in which the molecule could rotate" such that it gains the same amount of potential energy.

I have two questions...

Why does a molecule "gain potential energy" when it rotates? Does it want to stop rotating for some reson?
What do degenerate energy levels correspond to physically in terms of the molecule's rotation?

Thanks!


texts: Desorption instead of adsorption from solution using activated charcoal

texts:
I was just trying to see the effect of concentration on adsorption in solutions, i.e. I was trying to verify the Freundlich isotherm. I used oxalic acid and a batch of homemade activated charcoal (using this site).

First I prepared solutions of different concentrations. Then I added the activated charcoal, stirred it for 5 minutes and filtered the solution. When I titrated the filtrate using KMnO4, after calculating the concentration, I found that the concentration of the solution had been increased!

I tried the same process with different concentrations of oxalic acid solution and the result was the same. Can anyone tell me where did I go wrong?

Note: I used the same batch of activated charcoal in all the experiments. (Even then, how did the concentration of the solution increase? Shouldn't it be the same or lower than the initial concentration?)

For titrating oxalic acid, I heated the solution to about 60 degrees C.( After filtering the solution)


texts:
I know what demethylation is.

I have no idea what mono- means, the N is nitrogen of course, I know that from the line structure image in front of me if I could not guess it - and after quite a bit of google searching I gave up and came here.

Chemistry is not my field but out of curiosity and for no practical purpose whatsoever I started learning a few things outside my field, and I came across this tiny little naming issue. I thought this is so simple I could easily find something, but apparently it is even MORE simple than I thought - meaning everybody uses the term but nobody bothers to explain it. :-(


texts:
I think I'm making this more complicated than it needs to be, but here it is:

I have 7 drug solutions, all 1 mg/mL which need to have the following concentration in urine:

A: 25,000 ng/ml

B: 25,000 ng/ml

C: 100,000 ng/ml

D: 100,000 ng/ml

E: 10,000 ng/ml

F: 1000 ng/ml

G: 1000 ng/ml

How much of each 1 mg/ml solution do I need to add to urine to get a stock with the above concentrations? My ultimate goal is to take several 75 ul aliquots of urine for testing. Any suggestions?


texts: Why does reducing pressure cause the equilibrium to shift towards the side with less moles?

texts:
Take the example:

$$\ce{N2(g) + 3H2(g) <-> 2NH3(g)}$$

I understand that if I increase the pressure of the system, it'll shift towards the $\ce{NH3}$ side. This is because of the reaction rate increasing (increased collisions) more for the forward reaction than the reverse reaction. What I don't understand is why a decrease in pressure of the system would shift the equilibrium to $\ce{N2(g) + 3H2(g)}$. There is overall less collisions, but there's still more moles of reactants to collide and less molecules for $\ce{NH3}$ to collide and decompose.


texts: Including H⁺ from the dissociation of the acid in a titration pH calculation?

texts:
Let's say you are doing a standard titration problem, for example:

  Find the pH after adding $10~\mathrm{mL}$ of $0.3~\mathrm{M}$ $\ce{NaOH}$ in the
  titration of $25~\mathrm{mL}$ of $0.3~\mathrm{M}$ $\ce{HF}$ with $0.3~\mathrm{M}$ $\ce{NaOH}$.
  The $K_a$ of $\ce{HF}$ value is $6.6 \cdot 10^{-4}$

Most sources start by considering the reaction between $\ce{HF}$ and $\ce{OH^-}$, finding the pre-equilibrium concentrations of $\ce{HF}$ and $\ce{F^-}$ and then using Henderson-Hasselbalch or the equilibrium expression directly to find $\ce{[H^+]}$ (as seen here).

However, don't you have to consider the dissociation of $\ce{HF}$ first,

$$\ce{HF <=> H^+ + F^-}$$

and then consider the reaction between those produced $\ce{H^+}$ and the added $\ce{OH^-}$? Because whenever an acid reacts with a base isn't it truly the hydrogen ion formed from the deprotonated acid reacting with the hydroxide ion from the base? How can you consider reactions of unprotonated acids/bases directly?


texts: Can these changes be reversed by changing temperature?

texts:
An egg turning hard when boiled.
A spoon full of batter cooking on a hot griddle.

I said that they both cannot be reversed, because I think if you throw both the egg and batter into the freezer, it will freeze, but it will not be in its original form before you cooked both of them. Then again, I guess I could try this for real on my own but I don't know if that would be a good idea...


texts: How ‘lively’ would this ‘health’ potion be?

texts:
I’ve stumbled across a rather peculiar recipe for a allegedly ‘health’ potion in a computer game, composed of an unspecified amount of each of the following:

rust (iron oxide)
saltpetre (potassium nitrate)
oil of vitriol (sulphuric acid)
aqua vitæ (ethanol)

To make things clear: I’m not suicidal, I do in no way intent to actually mix that stuff (the initial tagging was maybe a bit misleading), but I’m interested in what would happen if someone actually would.  Drinking such a potion vile concoction is of course out of the question because of the sulphuric acid alone.

From what I know from highschool chemistry (and a generous helping of Wikipedia), saltpetre and sulphuric acid would be used to make explosives by way of nitrosulphuric acid.  Oversimplifying, by adding cellulose or tuluol one would end up with nitrocellulose or TNT, respectively.

But I lack the terminology to go further than that.  What would be the result of adding alcohol to that, and then iron oxide, or the other way round?  Is there some known mixture that would fit, however roughly, along those lines?  From the context of where that formula came from that wouldn’t surprise me.  It may of course as well be that the formula was simply chosen because of it’s obvious unhealthyness.

I hope this clarifies the intent of my question.  The idea may have come from a pseudo-fantasy/alchemy setting, but I’m interested in the ‘real’ chemistry behind it.


texts: Using PV = nRT to solve an electrolysis problem

texts:
Question: Two electrolytic cells are connected in series (the same current passes through each cell). One cell for the electrolysis of water produces $\pu{100 cm^3}$
of oxygen, measured at $\pu{273 K}$ and
$\pu{1.01
×
10^5
 Pa}$
. The second cell contains molten lead(II) bromide,
$\ce{PbBr2}$.
Determine the mass, in $\pu{g}$, of lead produced.
My working: $$PV=nRT$$
$$n={PV\over RT}$$
$$n\pu{={(1.01 \times 10^5)(100 \times 10^{-6})\over (8.31 \times 273)}} $$
$$\pu{= 4.45 \times 10^{-3} moles}$$
$$\pu{mass = 207.2 \times ANS = 0.922 g}$$
The given solution is:

Why do I have to multiply by 2 - what is wrong with my method?


texts:
Are there any generic rules / heuristics to identify a good GC vs a bad one?

The context is that during manufacturing-troubleshooting I often get shown GCs of various fine chemicals and I often wonder whether a problem is truly process-related or merely just an artifact of a bad GC operator / column / instrument etc.

Are there any benchmarks or signs to look for that will give a hint that a particular GC wasn't very reliable etc?

For example I've added one such GC graph below. Are there things too look for? e.g. I suppose non flat baselines or clamped off peaks are obviously bad? Merging peaks too? What else?


texts: Product of an intramolecular aldol condensation

texts:
When nonane-2,8-dione is treated with base, the product 1-(2-methylcyclopent-1-en-1-yl)ethan-1-one forms according to the following scheme: The arrow denotes the hydrogen that is first attacked by the base. But why does the reaction not take place like this? —
Why is the arrow-marked hydrogen less acidic than the previous one?


texts: Find gas pressures of injection knowing mixture pressure without knowing volume

texts:
Let's say we have a gas 1 moving inside a pipe (we don't know the geometry) at mass flow rate $Q_1$ and temperature $T_1.$ We inject a gas 2 at some point inside the pipe with gas 1 at mass flow rate $Q_2$ and at temperature $T_2.$
We know that the resulting mixture is moving at the mass flow rate $Q_\mathrm{mix} = Q_1 + Q_2$ at the temperature $T_\mathrm{mix}$ and is at pressure $p_\mathrm{mix}.$ All gases are ideal gases.
Is it possible to find the gas 1 pressure $p_1$ and the gas 2 pressure $p_2?$ And if so, what is the relation?
So far I haven't found any clues to solve this problem.
I thought about partial pressure, but I feel wrong to say that $p_1$ and $p_2$ are respectively equal the partial pressures of gas 1 and gas 2 in the gas mixture because there is no mention of volume in this problem.


texts: What is the direction of the net electric dipole moment in hydronium H3O+?

texts:
Assuming electric dipole moment points towards the negative charge, what would its direction be in hydronium?
Although the bonding electron density is distorted towards the more electronegative oxygen, it already has a formal charge of +1. Assuming the partial charge on oxygen due to distorted shared e.density is less than O.5, wouldn’t the actual electric dipole moment points away from the oxygen(opposite to distortion)? I can’t find any source to check this


texts: The transition metals have valence and penultimate shell incompletely filled . so does this mean that the transition metals first fill up their valence shell and then penultimate shell?


texts: Compound having the highest enol content will be?

texts:
The answer written in book is 3 but no solution is given.
After referring to some other question I think that hydrogen bonding can take place in compounds like 3 but am not sure about it. Am I right that it is the only reason why it has the highest enol content?

I would like to ask one more thing that, while comparing the keto and enol content, if in a compound more than one ketone is present, than do we enolize any one of them only to check?


texts: Structure-Activity Relationship of Chlormephos and Parathion

texts: According to the book "The Chemistry of Organophosphorus Pesticides", the insecticide Chlormephos (S-(chloromethyl) O,O-diethyl phosphorodithioate) has an oral LD50 in rats of 7 mg/k. According to that same book, the oral LD50 in rats for parathion is 6.4 mg/kg, making chlormephos about on par with parathion in terms of toxicity. Both of them work primarily by inhibition acetylcholinesterase. Both of them would presumably require metabolic activation due to the presence of a P=S bond. Despite their similar toxicities, their leaving groups differ significantly. So, my question is: How do the structures of chlormephos and parathion and their leaving groups in particular influence their toxicity, and why are their toxicities similar?


texts: What makes metals malleable and ductile?

texts:
Two well-known Physical Properties of metals is that they are malleable and dutile

I was just wondering about what causes metals to be malleable and/or ductile and non-metals to be brittle? What factor determines this?

Thanks!


texts: What symmetry elements mustn't a molecule possess to be considered achiral?

texts: Undergraduate textbooks say that a molecule mustn't posses a reflection plane and an inversion center to be considered achiral. As mentioned by Ron in his answer to this question, molecules that don't possess a plane nor center of symmetry, but do possess an $S_4$ improper axis are considered to be achiral. Are there any other symmetry elements that need to be taken into consideration when determining whether a molecule is chiral or not?


texts: Iodometric titration of copper – standard electrode potentials

texts:
Upon inspection of the standard electrode potentials for the half reactions for both $\ce{Cu^2+}$/$\ce{Cu+}$ and $\ce{I2}$/$\ce{2I-}$, it becomes apparent it should be the iodide ions that act as the oxidising agent, as the standard electrode potential for the iodine half-cell is much higher.
$$\begin{alignat}{2}
\ce{Cu^2+ + e- \;&<=> Cu+}\quad &&E_\text{cell} = +0.159\ \mathrm{V}\\
\ce{I2 + 2e- \;&<=> 2I-}\quad &&E_\text{cell} = +0.54\ \mathrm{V}\\
\end{alignat}$$

To explain this, many websites that I’ve looked at suggest it’s the weak solubility of copper(I) iodide, increasing the $\ce{Cu^2+/Cu+}$ potential to around $+0.88\ \mathrm{V}$.

Such websites include:

http://www.titrations.info/iodometric-titration-copper
http://chemistry.tutorvista.com/analytical-chemistry/iodometric-titration.html

What I’d like to know, is how this value of $+0.88\ \mathrm{V}$ has been determined, and a little of the theory behind as to why it has increased from $+0.159\ \mathrm{V}$.


texts: What are the blocks of the periodic table? What is the purpose of naming the elements per block group? What do they signify?


texts:
I was studying for my freshman chemistry course, and ran into a mind-boggling contradiction.

We know, at equilibrium, entropy is at a maximum:
$$\left(\frac{\partial S}{\partial V}\right)_U=0$$

From the first law

$$dU=TdS-pdV$$

which leads to

$$\left(\frac{\partial U}{\partial S}\right)_V=T$$

From the cyclic rule

$$\left(\frac{\partial U}{\partial V}\right)_S\cdot\left(\frac{\partial V}{\partial S}\right)_U\cdot\left(\frac{\partial S}{\partial U}\right)_V=-1$$

$$\left(\frac{\partial U}{\partial V}\right)_S=-\left(\frac{\partial U}{\partial S}\right)_V\cdot\left(\frac{\partial S}{\partial V}\right)_U$$

Using the result ($\left(\frac{\partial U}{\partial S}\right)_V=T$) it gives

$$\left(\frac{\partial U}{\partial V}\right)_S=-T\cdot\left(\frac{\partial S}{\partial V}\right)_U$$

But we know that $\left(\frac{\partial S}{\partial V}\right)_U=0$, so

$$\left(\frac{\partial U}{\partial V}\right)_S=0 \tag{1}\label{eq1}$$

So far so good.

Writing the total differential of $U$

$$dU=\left(\frac{\partial U}{\partial S}\right)_VdS+\left(\frac{\partial U}{\partial V}\right)_SdV$$

and comparing it to

$$dU=TdS-PdV$$

We get:

$$\left(\frac{\partial U}{\partial V}\right)_S=-P$$

Now I'm in real trouble, because equation $\eqref{eq1}$ says this quantity is zero, and even in this general series of thermodynamic equations, I have reached the conclusion that

$$P=0\,\,\,\,\,\,\text{(?!)}$$

I would appreciate if someone could help identify what the fundamental problem is? I've checked and rechecked my calculations and assumptions, but I'm sure I'm missing something.


texts: Why are fluorides more reactive in nucleophilic aromatic substitutions than bromides?

texts:
In nucleophilic aromatic substitution reactions, why do fluorides react faster than bromides?

Ordinarily bromide is a better leaving group than fluoride, e.g. in $\mathrm{S_N2}$ reactions, so why isn't this the case here? The only thing I can think of is that fluorine is more electron-withdrawing (via the inductive effect), which could stabilise the Meisenheimer complex formed as an intermediate.


texts: Steady state approximation for three-step cycle

texts:
How to write the steady state for $\ce{A}?$
$$\ce{A ->[$k_1$] B ->[$k_2$] C ->[$k_3$] A}$$

Species $\ce{A}$ seems to appear on both side of equation as it uses itself to produce some of itself. I have checked some online tutorials but I found none cover this scenario.


texts: Why is the carbonyl IR frequency for a carboxylic acid lower than that of a ketone whilst an ester is higher than a ketone

texts:
The approximate stretching frequencies are as follows:

  Acid: $1710$, Ketone: $1715$, Ester: $1730$ (all $\mathrm{cm^{-1}}$)

This would seem to suggest that the acid decreases the carbonyl bond strength and the ester weakens it. This must be as a result of the fact that in the ester inductive withdrawal is more effective than resonance and the converse is true in the acid. However, I am finding it hard to reasonably justify why. Presumably this is also linked to the relative electrophilicity of the ester and the acid.


texts: Is sulfuric acid or hydrochloric acid stronger?

texts:
Of my belief, sulfuric acid might be a little stronger than hydrochloric acid. Because even though they both are strong acids, one mole of sulfuric acid produces two times as much $\ce{H+}$ as one mole of hydrochloric acid.

Am I wrong?


texts: What forces keep a cotton fiber together?

texts:
According to Wikipedia, a single cellulose molecule is:

  a linear chain of several hundred to many thousands of β(1→4) linked
  D-glucose units.

which means a cellulose molecule is made of ~1μm of glucose units.

According to Trotman, 1984,

  Each cotton fibre is a unicellular hair [...] Each fibre, however long
  or short it may be, consists of one single complete vegetable cell
  [...] Average fibre length 13-51 mm.

  (6th ed., pages 27-33)

  (source: Trotman, page 31)

So if cellulose molecules are only ~1μm in length, what forces keep the cellulose molecules together inside the S1,S2,S3 structures throughout the fiber? How ~1μm units end up giving cotton its mechanical properties?


texts: Is the notion of orbitals different in theoretical chemistry?

texts:
I am just an average chemistry student that is currently exposed to theoretical chemistry. And I am seeing very puzzling things, such as 1p, 2f, 3g orbitals. In my attempt to reconcile this, I was thinking perhaps these are just so-called additional basis functions that are included in the calculations to better approximate the electron behaviour. Would that be correct?

Additionally, there is this idea of single-electron wavefunctions and N-electron wavefunctions, but no double-electron wavefunctions. Does this mean that there are only 1-electron orbitals in theories like DFT and HF, and no 2-electron orbitals?

This is rather weird because both these theories in theoretical chemistry and the the theory that we have learnt in high school (i.e. the theory of atomic structure that most students would know) are based on the same foundations of quantum mechanics. So how can they be so different? Could someone help to reconcile these differences?


texts: Which gas among radon and hydrogen chloride has higher ideal behavior?

texts:
Which one among the following shows maximum ideal behaviour?

$\ce{NH3}$
$\ce{HCl}$
$\ce{Rn}$
$\ce{H2O}$

Ammonia and water have hydrogen bonding so they're ruled out. That leaves radon and $\ce{HCl}$. Radon is a noble gas which means inertness but it's too big in size. That could mean greater van der Waal forces. And $\ce{HCl}$ on the other hand has covalent bonding.
I want to confirm which one of them is more ideal.


texts: How can the formula of WD-40 remain a trade secret?

texts:
Wikipedia says

  WD-40's formula is a trade secret

How can it remain a secret today? Can't mass spectrometers, NMR and other equipment be used to determine the structure of the compounds that go into it?

To put the value of the secret into perspective, the WD-40 company (whose flagship product is its namesake) makes \$76M a year and is currently worth \$2.7B


texts: Why does the internal energy increase when ice melts to give water?

texts:
Ice melts at 0 °C to give water at 0 °C. The internal energy apparently increases. Thermal energy is transferred to ice causing this to occur. Since the temperature doesn’t change, all the thermal energy is used to increase the potential energy(is this correct?).
Now I know that water is MORE dense than ice. Considering that, shouldn’t the potential energy DECREASE when ice melts? Consequently, shouldn’t the internal energy decrease?


texts: Nuclear power: what material is the control rod made from?

texts: What type of material is used in the control rod of a nuclear reactor? (Nuclear power plant)


texts:
I have two books on inorganic chemistry, one says that ortho hydrogen is more stable while other says para is more stable. Even on Internet, there are websites some supporting the former fact and some the latter. So, which one is more stable?
I think that para hydrogen is more stable because opposite spins cancel each other's magnetic effect, hence leading to lower energy (it's purely a guess, I'm not at all familiar with spin or magnetism) and if my answer is incorrect then what explains the stability of correct spin isomer?


texts: What is the difference between autocatalysis and self-replication in terms of chemical terminology?

texts:
I want to know does any difference between the meaning of autocatalysis and self-replication exist in modern chemical terminology?

E.g. I want to know can both terms be used interchangeably for entities requiring the presence of themselves in a reaction environment to catalyze the formation of themselves or is there any experimentally conceivable differences between molecules capable of autocatalysis and the self-replication of entities (therefore the category includes both molecules and larger complexes of molecules) in terms of the science of chemistry?

I want to know is the definition of autocatysis versus self-replication a problem of clarification of definitions-e.g. a problem of philosophy or is there any real-world experimentally identifiable difference between the 2 process in terms of chemistry?


texts: During phase change in matter, why doesn't the temperature change?

texts:
I was working on something in school and came across the question:

  Why does the temperature not change much during a phase change?

I'm really not sure why this happens in matter and I couldn't find an answer in my school resources. Does anyone here know?


texts: How can placing a lone pair in axial position differs from that in equatorial in number of electron domains?

texts:
I need help understanding the following statement in my book (regarding trigonal bipyramidal geometry):

  Placing a lone pair in an axial position would put it at 90 degree to three other electron domains. Placing it in an equatorial put is at 90 degree to only two other domains, thus minimizing the number of strong repulsive interactions

What does it mean by "90 degree" to two/three "domains"?


texts: What is hyperconjugation and how do you know if there is hyperconjugation in a compound? Which orbitals are involved in hyperconjugation?


texts: Can we use PV^y = constant equation for irreversible adiabatic processes?

texts:
Example: One mole of monoatomic gas expands at initial temperature $T$ at constant external pressure of $\pu{1atm}$ from $\pu{1L}$ to $\pu{2L}$.
To find final temperature, why can't we use $PV^y$ or $TV^{y-1} = \text{constant}$?
I am able to get final Temperature using $W+U=0$.


texts: Disposal of Silver Halides dissolved in Ammonium Hydroxide

texts:
I was reading the Lab Manual for Chemistry prepared by the NCERT . While going through the the test for Chloride ions (pg 88) I came across the following Hazard Warning :

The solution obtained after
dissolving AgCl/AgBr/AgI
precipitate in ammonium
hydroxide should be
acidified with 2M HNO3
and should be discarded
quickly to avoid serious
explosion.

How does it cause a serious explosion?


texts: How to find the number of stereoisomers of a tetra-substituted allenes, exhibiting both axial and central chirality?

texts:
I need a reliable method for determining the number of diastereomers and enantiomeric pairs of the following series of compounds bearing in mind that the substituent groups A are chiral on their own (exhibiting central chirality).

There are two planes of interest bisecting the allene sistem, the one constains the left A groups, the other is orthogonal to it. If two A groups are to be reflected through one plane (so it becomes a symmetry plane) their configuration must be different. That is all regarding the central chirality, but I don't know how to include axial chirality in this description (so I don't count one stereoisomer twice).

I think that these are the four diastereomers. Instead of A, I wrote the configuration of A (R/S). Now, as R and S are connected with a mirror plane, diastereomers 2 and 4 shouldn't exhibit axial chirality, as R and S can be regarded as same substituents on one side of the allene system (because of the mirror plane). That's why the third diastereomer exhibits axial chirality (P/M). I am not sure whether my reasoning is correct. The rest beats me. The answer should be 4 diastereomers and 3 enantiomeric pairs (last page), but how?


texts: Benzenesulfonyl chloride dehydration of an amide to give nitrile

texts:
1) I am unable to understand how benzenesulfonyl chloride acts as a dehydrating agent in dehydration of amides? What is the driving force for losing chloride and taking the oxygen from the amide?

2) Why I can't use other dehydrating agents like $\ce{P4O10}$, $\ce{H2SO4}$, or $\ce{CaCl2}$?

3) How can I estimate what is suitable dehydrating agent for a particular reactant?

4) Is it necessary to use only those dehydrating agents that undergo chemical change? Or can I use dehydrating agents that adsorb water like silica gel?


texts: Combining Bond Enthalpies and Enthalpies of Formation

texts:
Can I mix formation enthalpies and bond enthalpies in the same calculation?

I think the answer is no, since they are relative measurements, and possibly relative to different things, but I haven't seen it stated explicitly anywhere.


texts: Mechanism of Oxymercuration-Demercuration reaction

texts:
I am trying to write a mechanism for OMDM reaction.

I could write the mechanism for oxymercuration part of reaction but I couldn't write the mechanism for remaining part (demercuration) of the reaction. Could anybody help me to proceed forward.


texts:
Specifically, instead of its normal structure, this Lewis structure seems to be valid as a constitutional isomer:

$\ce{Cl-O-S-Cl}$

So what prevents this from existing, or if it already exists how is it made?


texts:
I am trying to analyze the $\sigma$ orbitals of benzene molecule using group theory, doing the same thing that is done to the $\pi$ orbitals. The symmetry group of benzene is the $D_{6h}$; considering the $sp^{2}$ orbitals of the benzene:

and applying the symmetry operations to these orbitals, I can find the caracters of the representation with which they are transformed, and I can decompose this representation in the irreducible representation of the group. Doing this, I found

$$\Gamma = 2 A_{1g} \oplus 2E_{2g} \oplus B_{1u} \oplus B_{2u} \oplus 2E_{1u} $$

Now, I can construct the projection operators and with them I get the symmetrized orbitals for each representation. The molecular orbitals will be the linear combinations of these orbitals. My question is: In which function should I apply the projection operators? In the $sp^{2}$ function?


texts: Rate of aromatic nucleophilic substitution reaction on ortho and para fluoronitrobenzene

texts:
Why rate of aromatic nucleophilic substitution of Ortho-fluoronitrobenzene is greater than para-fluoronitrobenzene?
Kindly note question is about why rate of ortho is greater than para position. Not meta position.
This is previous year KVPY question but they had not asked reason and just asked comparison of rate.


texts:
hopefully this question is in the right place.

I'm a biologist not a chemist (so sorry if this is a stupid question!)- I'm doing some RNA extractions from brain tissue which requires the use of Chloroform. In the manual, it specifies:

Chloroform must not contain isoamyl alcohol or other additives and must be pure.

This is what it says on the label:

Does this count as 'pure'? Obviously pure is quite a subjective term, but it doesn't to my eye contain any isoamyl alcohol, so I suspect it should be OK - but I thought it best to check.


texts: Ethanol and water hygroscopic equilibrium concentration

texts:
I am working with a company to help improve their reaction process where they use SDA 2B Alcohol (Karl Fischer titration has it at 99.66% EtOH, 0.3375% toluene). Specifically, I am attempting to determine what theoretical %wt or %vol of water is pulled from atmospheric air into pure ethanol given an infinite amount of time? Does it ever reach an equilibrium state and, if so, what is it?

My gut guess is ~95.5%wt EtOH/4.5%wt H2O, the azeotropic concentration.

Assume constant relative humidity and room temperature. The ethanol is stored in a closed tote (~220 gallons). Initially, the tote is full of as-shipped ethanol (negligible air volume). However, half the ethanol is removed as part of a batch run. So, really, what I'm trying to get at is what happens to the leftover ethanol that is now sitting in a closed tote with ambient conditions.

Please let me know if additional details will help answer the question. Thanks!


texts: In equilibrium, if bonds are constantly being created and broken, where does the energy that does so come from?

texts: I'm a student who recently learned about equilibrium and how it is not a state where nothing is made, but rather, a state where the product is decomposing at the same rate as the reactants are combining. If breaking and creating bonds takes energy, where does this energy come from? Does it have to be added to the system? Also, if a closed system, say, a glass jar, reaches equilibrium, and heat slowly leeches out of the jar, does the balance of equilibrium shift, or does the reaction slow down but stay in equilibrium?


texts: what is the difference between a redox reaction and an ionic bond?

texts:
I am new into chemistry...
I'd like to know what the difference is between an ionic bond: which involves a bond with an electron transfert, and a redox reaction; which seems to be exactly the same to me.

Thanks


texts: I was given an assignment to find out if sand is a mixture or a compound I'm sure it can't be an element. Considering the fact that a mixture contains two or more substances that are not chemically combined and not proportionally fixed and a compound is contained substances that are chemical combined and are fixed proportionally. Sand contains a lot of divided small rocks and mineral particles.


texts:
I need to distill some reagents, and the book Purification of laboratory chemicals suggests first refluxing over $\ce{P2O5}$ for several hours before distilling across.

The obvious choice is a solvent still head like the ones used to distill THF, but I don't need very much of this so it seems wasteful.

The way suggested that I do it is to set up a normal reflux, let it cool, and then quickly change the condenser for a side arm. This will obviously work but seems like a lot of effort. I think there should be some other piece of glassware to allow this process. Is this the case?


texts: Cyclohexene reduction reaction with hydrogen gas and ethanol

texts: I have a following reaction (see below). I found the section of reduction and oxidation states in my book but there is nothing about cyclohexenes. I know that the double bond will be reduced in this reaction but what I have no idea what happens to those substituents. Why do they move around and what are their orientations?


texts:
I've read that radioactive compounds are dangerous because they emit electromagnetic waves (gamma-radiation etc.) that are dangerous for living organisms because they can ionize atoms in molecules.

So if one water molecule is ionized by using radiation, would you then get:

$\ce{H2O -> H^+ + OH^-}$
or would you get free radicals : $\ce{H2O -> H^{.} + OH^{.}}$?


texts: $P 4_{2} 22$ tetragonal group choice of origin for symmetry of special projections

texts:
I was looking at the description of the tetragonal group $$P 4_{2} 2 2$$ (No 93 in the International Tables of Crystallography) and there is one aspect that I do not understand. Namely, what is the convention and implications of choosing the origin point? For example, for the two fold rotation along the [110] plane, the origin is choosen to be $$(0, 0, \frac{1}{4})$$ and thus we should have the following transformation:
$$x \rightarrow y, y \rightarrow x, z \rightarrow -z + \frac{1}{2}.$$
Why the origin is not set at $(0, 0, 0)$ and then one would have:
$$x \rightarrow y, y \rightarrow x, z \rightarrow -z?$$


texts: What function is used to graph the potential curve of two hydrogens with parallel spins?

texts:
TL; DR
I am asking for

an analytic potential curve function for the triplet state of $\ce{H2}$ (preferred) with experimental parameters, or
experimental data (enough points to realise a smooth-looking curve).

Also see solid red curve pictured below.

To characterise the energy of a two-atom system, Morse potential is applied as a second approximation after the harmonic oscillator model. This is an analytic function of the form $$E=D_\mathrm{e}\left\{1-\exp[-a(r-r_\mathrm{c})]\right\}$$
where the parameters $D_e$, $a$ and $r_c$ depend on the atoms in play. Surely enough, better results are achievable. For examples on simple molecules, I found the paper by Hulburt and Hirschfelder, 'Potential Energy Functions for Diatomic Molecules', J. Phys. Chem., ($1940$) to be rather useful. Have a look at equations $(14)$ and ($15$) specifically (available more easily here). The one I used was

$$E_{\mathrm{P}}=\mathrm{D_e}[(1-\mathrm{e}^{-z})^2+\mathrm{c}x^3\mathrm{e}^{-2z}(1+\mathrm{b}z)],$$
where
$$z=\frac{\omega_\mathrm{e}}{{2}\sqrt{\mathrm{B_eD_e}}}\left(\frac{x-\mathrm{r_0}}{\mathrm{r_0}}\right)$$

This is for the case where spins are antiparallel.
If atoms of parallel spin approach one another, the qualitative picture is quite different. A smaller distance will equal higher energy regardless of separation, i.e., no stable equilibrium state exists. Unfortunately, finding a nice function for the antibonding situation proved less fruitful. An example of what I'm after is the solid red curve found in this Wolfram demonstration.


texts: Does the amount of acid change when I add water to vinegar?

texts:
I have a question that asks me to describe why adding distilled water to my vinegar sample would not affect my calculated Molarity (determining amount of acid in the vinegar be titration with a base).

At first thought, it wouldn't, because the same amount of acid is still there, we'll still have the same amount of base reacting. So you'll still get the same amount by measuring how much base was needed.

But that got me thinking. There is a lot of diluting acids with water, but isn't water amphiprotic? Why doesn't it react with the acid, or react with it enough to matter at least? What information am I missing here?


texts:
I am trying to create the molecule of the methylcyclohexane in the equatorial and axial conformers. I read in this site about the chair conformation. My molecule looks like the following picture (created in Molden)

Can someone point out if this is actually good? I am quite doubtful about the "mid" carbons, should they be push to the center of the molecule like in the drawings in the website?


texts: How should I modify my molecular dynamics simulation so that known chemical reactions can be modelled?

texts:
I have written some molecular dynamics code that I want to use to model known chemical reactions.

By known I mean that it has been observed in a lab that $\ce{A +B->C}$.

I am not interested in finding out if it is feasible that two things react (i.e. is there a favorable energy configuration?), rather I am interested in finding out what the concentration over time looks like given a volume, concentration, temperature and a pair of chemicals that I know will react.

At the moment I just check if they are very close to each other. This produces reasonable looking concentration curves.

Is this is a correct way of doing things? I am looking for publications so it has to be defend-able, not just OK.

I am also interested in modelling large bio-molecules in a coarse grained simulation.

Are there any particular potential functions that I should use for large biomolecules, or will LJ do?


texts: How to assess sunscreen effective via blueprinting?

texts: How do I assess the effectiveness of sunscreen creams by using the blueprinting process? I know blueprinting is done when something is sensitive to light and this may cause reactions to produce a product that causes Prussian Blue to appear. However I am unsure how to connect sunscreen and blueprinting - does it have to do anything with the colour in relation to its wavelengths and how it is connected to UV light?


texts:
I'm confused on what a triglyceride is, from what my text book it says its a type of gylercide, then from a website it said

  Glycerides can be subdivided into two categories. The first group, the neutral glycerides are nonionic and nonpolar. The second group, the phosphoglycerides contain a polar region, the phosphoryl group.

Which makes triglyceride not a directly under a glyceride but under one of these groups. Then it says

  Esterification may occur at one, two or all three positions producing monoglycerides (monoacylglycerols), diglycerides (diacylglycerols), or triglycerides (triacylglycerols). The most prevalent and most important are the triglycerides.

So does that mean that triglyceride can be produced by either of the two groups phosphoglycerides and neutral glycerides. And if that's correct then how are monoglycerides and diglycerides produced.

Source


texts: Could anyone suggest some catchy chemistry experiments or demonstrations, to be performed in front of a young audience?

texts:
I'm wanting to volunteer at some of our local children centers, and do some experiments to interest them in Science/Chemistry. One cool, flashy experiment is to light my hand on fire - and not have to go to the hospital after.

The general scheme I've found for it (I've not tried it - and the instructions aren't .edu or other '95% correct' sites, so if you know of any corrections for this please chime in) is:

50 - 50 EtOH and Water, plus a small amount of salt for color. Dip your hands in, light them on fire, the EtOH burns coldly enough that the water doesn't evaporate and your hand stays safe and insulated.

Of course, I'll test it on small scale on paper in lab first.

However, I'm initially hesitant to play with fire around children. For obvious reasons.

Does anyone have anything similarly flashy or attention grabbing that they've used for a similar purpose with children? Obtaining restricted materials isn't an issue, but low-cost is preferable.

Note: I know this stackexchange frowns upon questions that don't have a specific answer, with the rules stating that discussion type questions are non-preferred - but this question isn't for the meta site, and I trust this community of educated scientists to have better advice on experiment safety than say, the educator stackexchange, so forgive me if this doesn't fit the general site mold.


texts: How do Precipitation Reactions behave in the Absence of Gravity?

texts:
How do precipitation reactions behave in the absence of gravity, say on the International Space Station (ISS)? I have seen water taking the shape of a sphere and not that of the container in space due to its surface tension. It takes a spherical shape in order to minimize the energy due to forces of surface tension. In space all directions are equivalent and hence there is no notion of up or down.

In precipitation reactions, generally, the precipitate formed either floats on the surface or settles down. I know the solid particles will be formed in space due to the chemical reaction between the reactants. What will happen to the solid particles (precipitate), will they concentrate at the centre of the sphere of the reaction mixture (solution) or will they come to the surface, or will they remain suspended, or is there any other possibility? Has such an experiment been done on the ISS to date?

For reference, this is how water looks in the absence of gravity:

Please note: Water is coloured to enhance visibility


texts: Is it possible to create an acid anhydride that's stable in water and if so what conditions must its structure satisfy?

texts:
I ask this question because if acid anhydrides are always unstable in water then my interest, as a student of pharmacology, would be greatly diminished. Acid anhydrides are, in my books, at least, the result of a dehydratation reaction between two carboxylic acids and hence their structures look like this:

Where R1 and R2 are organic substituents.


texts: Does PCl3 react with ester as it does with carboxylic acid to produce an acid halide?

texts: I did not find it anywhere in a book but I do wonder if it might react.


texts: Energy needed for electrolysis of aqueous NaBr

texts: I'm trying to find the amount of energy it would take to electrolyse sodium bromide to get 1 mole of Br2. I'm not sure how to go about calculating this figure. If anyone could help me out, I'd be very grateful.


texts: Which has a higher enol content between 4-Pyridone and Cyclohexa-2,5-dien-1-one?

texts: I am new to organic chemistry but here is what I feel. 4-Pyridone will have a lower enol content as in its keto form it has higher resonance stabilisation due to the involvement of lone pairs on nitrogen in conjugation while in the enol form the lone pair on nitrogen being in the molecular plane will not participate in resonance and thus will have an impact on resonance stabilisation. Thus the second compound(cyclohexadienone) will have higher enol content. Is my justification right?