All Questions

8
votes
3answers
1k views

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 ...
13
votes
1answer
239 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 ...
9
votes
1answer
4k views

Why are peroxides explosive?

Why do peroxides tend to explode with little provocation? In general, what are typical products of their explosion?
7
votes
1answer
20k 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 ...
14
votes
1answer
17k 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 ...
12
votes
3answers
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 ...
7
votes
1answer
914 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 ...
8
votes
1answer
196 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 ...
12
votes
5answers
114k views

What is a neutral atom?

Someone gave me definition of atomic number as follows: The number of electron or proton present in a neutral atom is called atomic number. It is represented by Z...
0
votes
2answers
3k 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?
37
votes
2answers
78k 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 ...
15
votes
2answers
14k 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 ...
8
votes
2answers
12k 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 ...
16
votes
1answer
1k 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, ...
8
votes
1answer
712 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.
11
votes
3answers
528 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 $\delta$ ...
37
votes
5answers
8k 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 ...
8
votes
1answer
357 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” ...
6
votes
1answer
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 ...
20
votes
3answers
2k 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% ...
7
votes
1answer
692 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 ...
32
votes
1answer
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 ...
20
votes
3answers
424 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 ...
7
votes
1answer
554 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 ...
7
votes
1answer
258 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 ...
10
votes
0answers
191 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 ...
10
votes
1answer
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?
7
votes
1answer
123 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 ...
10
votes
1answer
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 ...
8
votes
2answers
293 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 ...
8
votes
1answer
946 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 ...
12
votes
4answers
8k 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....
11
votes
2answers
11k 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?
4
votes
1answer
823 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 ...
9
votes
2answers
4k 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 ...
14
votes
6answers
48k 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 ...
5
votes
1answer
3k 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 = ...
5
votes
1answer
249 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-...
8
votes
2answers
354 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....
6
votes
1answer
134 views

Is there any danger of forming explosive reaction products during the electrodeposition in Diethylene glycol?

I know that perchloric acid could be potentially explosive and some organic solvents could form dangerous peroxides. I am going to do an electrodeposition in diethyleneglycol solution containing $\...
16
votes
1answer
641 views

Any false chemical element in history of chemistry?

Was there any false chemical element introduced in history of chemistry. I mean a substance that after a while proved that it was not an element.
14
votes
1answer
3k views

Synthesis of mandelic acid from benzaldehyde

For an upcoming exam, I have to describe the synthesis of 2-hydroxy-2-phenylacetic acid (mandelic acid) from benzaldehyde. The provided answers describe quite a long process, consisting of 8 stages. ...
0
votes
0answers
397 views

Basic chemistry equation with ammonia [closed]

A table in the book 'Chemistry NCEA Level 1' has 4 headings, the first of which is 'Volume (mL) ammonia solution provided (conc 2 g L-1)' Could someone please provide a comprehensive explanation of ...
16
votes
2answers
3k views

Liquid which neither dissolves in water nor oil

I am looking for a liquid which is not miscible (or very close) with water or vegetable oil. Ideally, I want to have a container which shows three layers (the three liquids) with clear boundary ...
7
votes
1answer
210 views

CHARMM parameter files for NBD (nitrobenzoxadiazole)

I have been looking all over the internet for forcefield parameters for a fluorescent probe called NBD (nitrobenzoxadiazole). Here is an example of an NBD labeled fatty. I have so far only found ...
5
votes
1answer
2k views

How would I calculate the Normality of a 0.00167 molar solution of KIO₃?

I need a 0.01 N solution of $\ce{KIO3}$ to use as a standard in a Winkler titration. The protocol that I am using specifies that this is 0.3567 g L-1, which I have calculated to be 0.00167 M based on ...
5
votes
1answer
741 views

Bond energies database

I’m looking for a public database of bond energies of biochemical compounds. Does one exist? Otherwise, which is the standard computational methodology to calculate them? Any references would be very ...
7
votes
3answers
11k views

Synthesis of chloroquine from 4-amino-7-chloroquinoline

Can we get chloroquine from 4-amino-7-chloroquinoline (7-chloroquinolin-4-amine) by adding 4-chloro-N,N-diethylpentan-1-amine $(\ce{CH3CHCl(CH2)3N(Et)2})$ ?
5
votes
1answer
118 views

Do Na or Li need heat in order to react with Cl₂?

I've read how putting a burning piece of sodium in chlorine would produce white $\ce{NaCl}$ fumes. However, I can't find out whether Na or Li can react with $\ce{Cl2}$ without heating or burning.
9
votes
3answers
594 views

MacGyvering a sealed tube

Is it possible (advisable?) to make a sealed tube by melting and twisting the end of a borosilicate test tube? One issue that I can think of is that the pressure might be too high if I then proceed to ...

15 30 50 per page