# All Questions

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### What is the correct name for this lab technique in crystallization?

Take a glass rod and rub vigorously the wall of the flask, the substance will crystallize out of the solution. Take a fire polished stirring rod and etch (scratch) the glass of your beaker. The small ...
252 views

### Why is mercury a "fancy proton"?

I remember that one of my old organic chemistry profs referred to mercury as being a "fancy proton". I think it was in the context of oxymercuration reduction. What might have been his rationale for ...
5k views

### Why are peroxides explosive?

Why do peroxides tend to explode with little provocation? In general, what are typical products of their explosion?
22k views

### Adulteration of turmeric with Metanil yellow

I read in the local paper that common food products like turmeric can be adulterated. It continued to specify the adulterant which they called metanil yellow. On searching on the Net, I was able to ...
23k views

### Why do aromatic hydrogen atoms have a higher chemical shift value compared to aliphatic hydrogen atoms?

In Nuclear magnetic resonance (H-NMR) spectroscopy, the chemical shift of aliphatic hydrogen atoms are very much closer to the 1.0 ppm than that of aromatic hydrogen atoms. Aromatic hydrogen atoms ...
8k views

### Calcium carbonate toxicity

I can't make heads or tails of the information on the net — although there seems to be plenty of it, it seems contradictory. Supposedly, calcium carbonate is used in antacids—yet there are warnings ...
960 views

### Where can I obtain tables of P-V-T/compression factor data?

Some recent research I'm dealing with has required me to look for tables of experimental pressure/volume/temperature values (equivalently, a table of compressibility/compression factors in terms of ...
307 views

### Difference between non-thermal and thermal ionized gases

Why or when does non-thermal plasma become thermal? How do we know before hand if the ion temperature will differ from the electron temperature, on what parameters does it depend - where is the ...
155k views

### What is a neutral atom?

I was told that an atom's atomic number is defined as follows: The number of electrons or protons present in a neutral atom is called atomic number. It is represented by ...
5k views

### Is carbon tetrachloride an electrolyte?

Is $\ce{CCl_4}$ an electrolyte all by itself, or does something need to be added to it so that it becomes an electrolyte? Also, is it weak or strong?
88k views

### Differences between phenols and alcohols

I know phenols are more acidic as compared to alcohols, but are they considered different from alcohols? Sure, you can study something as a subset, but are phenols considered a subset of alcohols, or ...
18k views

### Can I test for lead with household chemicals?

I picked up a metal fence loop cap today and took it home just because I liked the shape. (^ not mine) I cleaned it, but some of the paint is chipping off. I'm only vaguely thinking about lead, and I'...
13k views

### Temperature dependence in absorption spectroscopy

What are some qualitative guidelines one should know regarding the temperature dependencies (of the gas and maybe the radiation, if that makes sense) for an absorption spectroscopy measurement? How ...
2k views

### How to name this cyclic compound with an O in it?

How to name this cyclic compound with an O in it? I was going to name it cyclobutane, but not all of the atoms making up the ring are carbons, one is an oxygen. So, then I decided to name it butane, ...
753 views

### How does brewing time and brewing temperature affect the flavonoid concentration of green tea?

I've searched a lot for this, but I still cannot find any good explanations for how these two factors affect flavonoid concentrations.
726 views

### Are there any molecules with delta bonds in their ground states?

When looking at excited states of molecules, $\delta$ bonds are relatively common, but I've never come across a molecule with a $\delta$ bond in its ground state. Are there molecules with $\delta$ ...
12k views

### Fundamental forces behind covalent bonding

I understand that covalent bonding is an equilibrium state between attractive and repulsive forces, but which one of fundamental forces actually causes atoms to attract each other? Also, am I right ...
430 views

### Efficiency of various Ewald-type schemes for the summation of electrostatic interactions

I am looking into implementation of Ewald summation techniques for a number of point charges in periodic 3D space (i.e. a molecular simulation box with periodic boundary conditions). The “mainstream” ...
1k views

### How does temperature affect the concentration of flavonoids in orange juice?

I am in high school, and I would like to do an experiment on this for a project. I've done quite a bit of research into the different methods I could use (see 2.4.2 here) but I still cannot find ...
3k views

### 67 failures at extracting acetaminophen from Excedrin(R)

I have adapted the lab experiment described in this J. Chem. Ed. article for the organic chemistry lab course I teach. In the past year, the first year of implementation, I have had 67 failures (100% ...
904 views

### Test presence of oxygen > 1%

I want to qualitatively test for the presence of oxygen within argon gas. I would like the test to be positive if approx $1\%$ or more is oxygen, but definitely negative if less than $0.1\%$. Anywhere ...
1k views

### Flammability (NFPA) - how is it defined?

I was reading up on a wonderful little chemical compound known as chlorine trifluoride ($\ce{ClF3}$). For a primer, check out Dr. Derek Lowe's blog post here: Sand Won't Save You This Time. The title ...
528 views

### Energy-efficiency aside, what are the chemical constraints on CO₂ capture and methanation?

Synthesising $\ce {CH4}$ from air and water (in a non-biological process) has been proposed as one form of energy storage. What are the chemical constraints at play here? That is to say, what sort of ...
584 views

### How can one optimise the formation of copper acetate?

Mixing solid copper, $5\%$ vinegar, and hydrogen peroxide ($\ce{H2O2}$) causes copper acetate to form. The process will occur very slowly without hydrogen peroxide. Adding $\ce{H2O2}$ speeds the ...
342 views

### Negative retention for chloride in hydrolysate filtration

I tried to fractionate proteins as a function of their size with an ultrafiltration membrane. I observed a higher concentration of chloride in my permeate than in my feed or retentate. The proteins do ...
197 views

### Why are many drugs in the hydrochloride form? [duplicate]

Possible Duplicate: Why are solid phase organics often conjugated to HCl? I'm wondering why a lot of drugs are in this hydrochloride form. E.g., Cetirizine hydrochloride Methylphenidate ...
1k views

### Oxidative chlorination mechanism (sulfide to sulfonyl chloride)

I cannot find much guidance in the literature. Any ideas as to what the mechanism of this reaction might be?
134 views

### How do you determine the amount of acrylamide in foods such as baked fries?

There are many food studies which determine the concentration of a substance in a food item. For example, this study determines the concentration of acrylamide in solid foods like fries. By what ...
5k views

### Can class D fire extinguishers be used for other fire types than metal fires?

Burning metals like sodium should not be extinguished with standard fire extinguishers, but they require either sand or a special class D fire extinguisher. Now, if there is a fire in the lab and ...
385 views

### Are all cubic point groups encountered?

My symmetry lecture notes state that there are seven high-symmetry 3D point groups, which have more than one rotation axis of order greater than 2: $T$, $T_d$, $T_h$, $O$, $O_h$, $I$, $I_h$. I ...
1k views

### Does borax do anything more for "boosting" detergent than adding active oxygen would?

Borax, $\ce{Na2B4O7}$, is often marketed as a "laundry booster" under the brand "20 Mule Team Borax". The unit crystal of borax can be seen below. Other laundry products in the past have added ...
10k views

### The mole is used extensively in chemistry, why not elsewhere?

In chemistry, the unit "mole" is used in many places, and is an important tool when working with quantities. I have not seen it used elsewhere--for example, we never count people or TVs with the unit....
16k views

### Do hydrogen halides (HX) form strong or weak acids?

I know that when dissolved in water, hydrogen halides ($\ce{H-X}$), become acids. I know that $\ce{HF}$ forms a weak acid, but can it be generalized that all $\ce{HX}$ acids do so?
861 views

### How does a Brunauer–Emmett–Teller device function?

The Brunauer–Emmett–Teller (BET) theory is comprehensible. My question is more geared towards what is physically and chemically happening within a BET device to get a reading? How does a BET device ...
5k views

### Are there any general chemical rules for choosing initiators for a polymerization reaction?

I'm working with some very basic free-radical initiated polymerization reactions. For the most part, I just follow a recipe I'm given (by a member of my group or the broader literature), it works, and ...
51k views

### Handling and storing sodium hydroxide, hydrochloric acid, hydrogen peroxide and isopropyl alcohol

I'm an electrical engineering and I hope you can give me some advice as I'm not much into chemistry. I'm trying to start making my PCB (Printed Circuit Board) at home but I'd like to have some advice ...
4k views

### MO-Scheme of SCN- and its bonding properties when used as a ligand

I tried to figure out the MO-scheme of the tetragonal-bipyramidal complex trans-$\ce{[Co(en)2(NCS)2]SCN}$ in which the isothiocyanate ligands are bound to the $\ce{Co^3+}$-Ion in $\eta^{1}$-mode (en = ...
262 views

### What is the difference between an ionic and molecular activity model? (Example: Diopside-Hedenbergite)

Original question: When looking at a Diopside-Hedenbergite solid solution, what is the difference between an ionic and molecular activity model? Why does the moleclar model yield higher values? Post-...
450 views

### How to translate the mobile phase from thin layer chromatography to column?

I recently was told that once you find a good solvent mixture for separation on thin layer chromatography (TLC), you should only use 10% of the more polar solvent (for silica) when you run your column....