# All Questions

31,746 questions
Filter by
Sorted by
Tagged with
284 views

### Addition of NaCl and CaCl2 to snow

In cold countries, it is a common phenomena to add salt to melt or clear snow. However, only specific salts are being commercially. So my question is that why only sodium chloride and $\ce{CaCl2}$ are ...
2k views

### Chirality of buta-1,2-diene

My teacher says buta-1,2-diene is symmetric and hence optically inactive but I think it's the opposite, because allenes with an even number of double bonds are optically active because they have no ...
202 views

### Confused with oxidation numbers

If -2 is a oxidation number and 2- is the charge, then what is - by itself, is it a oxidation number or charge? As in $\ce{Ag+}$. Also do you see $\ce{Cu + 2Ag+ -> Cu^{2+} + 2Ag}$ as a redox ...
2k views

### Easy method of analysing iodine content in supplements?

Most health-food stores carry supplements supposedly containing iodine for people with iodine deficiency. I recently bought some kelp tablets that are supposed to have iodine but as a consumer how can ...
1k views

### Calculus and physical chemistry [duplicate]

Is calculus and differential equations really that useful in physical chemistry? How does knowing that helps me in physical chemistry? And how much of calculus must I know in order to do physical ...
63 views

### Searching for a solvate that changes its solvation property

I'm looking for a solvate that changes its solvation property when being dried. One example of such a material is gypsum: at temperatures up to 250°C it becomes γ-anhydrite which will slowly hydrate ...
165 views

### Dissociation of ligand

If a ligand K[Ag(CN)2] is dissociated.. Which one is correct dissociation equation? $$\ce{K[Ag(CN)2] -> K+ + Ag+ + 2CN^-}$$ or $$\ce{K[Ag(CN)2] -> K+ + [Ag(CN)2]^-}$$
3k views

### Boron trihalides acidity

Boron trihalides ($\ce {BX3}$) is a Lewis acid, because it can accept an electron pair, as Gilbert N. Lewis definition. Now my question is, please arrange ($\ce {BF3}$), ($\ce {BCl3}$), ($\ce {BBr3}$),...
179 views

### How to find trace methanol content in fermented fruit/distillate?

Suppose we have some fermented (optionally also distilled) fruit/fruit juice. The sample therefore contains water, sugars, ethanol etc. Which analysis method is the simplest to find out whether the ...
870 views

### What is the difference between the reactivity of Lead subacetate and Lead II acetate undergoing a hydrothermal process?

I am attempting to adapt a hydrothermal method for synthesizing $\ce{PbS}$ nanocrystals to my school that contains a mixture of cationic and anionic surfactants sodium dodecyl sulfate (.05 mmol, SDS) ...
52 views

### Modelling planar ring molecules and their evolutions [duplicate]

This is the next step of my previous question. I am trying to simulate a circular chain (ring) of molecules which are planar (two dimensional). What I do is take a planar unknot and embed it into a ...
9k views

### Hardness and softness are terms used to describe which aspect of acidic behaviour?

What do hardness and softness mean? Is it something to do with the polarisability.
1k views

### Oxalic acid structure

What is the reason why oxalic acid has its second $\ce{-COOH}$ group flipped? I'm guessing it's something to do with steric repulsions between the $\ce{-COOH}$ groups but I'm not sure.
776 views

### Heat of combustion per mole and per kilogram

I need to calculate the heat of combustion per mole and per kilogram of complete combustion of, say, X. I write reaction : $\ce{X + O2 -> ... + Q}$ Find Q using Hess law Now, what do I do after ...
6k views

### Stability of transition metals in aqueous solution

Which is more stable in aqueous solution: $\ce{Cr^3+}$ or $\ce{Mn^3+}$? Why? My approach: $\ce{Cr^{3+}}$ should be more stable as the $\ce{3d}$ electrons will enter the $\mathrm{t_{2g}}$ orbitals. ...
66 views

### Modelling planar molecules and their evolutions

I am trying to simulate a chain of molecules which are planar. Can anyone please give me an example of the molecular chain which can stay as planar with it's minimum energy state is planar. A ...
2k views

### Does Nitrogen dioxide change colour if we put it in a constant temperature of e.g. 100 kelvin?

The changing of the colour of $\ce{NO2}$ is because of a change in temperature, resp. heating and cooling?
149 views

### How do i detect the compounds a plant is made of, automatically?

Let's say I want to take a random plant , and get the chemical formulas of the compounds he's made of. Is there an automated method for doing so and how costly is it(roughly) ?
22k views

### How to determine the pH of a mixture of two weak acids?

We’ve two solutions: Solution 1 $\ce{HCOOH}$ its concentration is $c_1=10^{-2}\ \mathrm{mol/l}$ and its volume is $V_1 = 50\ \mathrm{ml}$ and its $\mathrm{pH}_1 = 2.9$. Solution 2 $\ce{CH_3COOH}$ ...
99 views

### How do I lookup a polymer by its structure?

This is more of a meta-chemistry question, but, here goes... Given the structure of a polymer, how can I search online for which polymer it is? Specifically, I have an image like this: I'd also ...
42k views

1k views

### Are there any safety guidelines for mixing sulfate with chloride?

Some ceramicists decorate pottery using soluble salts (usually chlorides and sulfates e.g. copper chloride, cobalt sulfate) which are used individually or mixed to produce different colors. I have ...
323 views

### Voltaic and electrolytic cells

Why more attractive metals will be oxidized? Aren't they being reduced, because they attract and receive electrons from negative polyatomic ions? So they will be anodes, where oxidization occurs. Why ...
112 views

### Why is it a good idea to put some salt in the bread dough?

The salt that you can typically find in a kitchen is the $\ce{NaCl}$, isn't this salt supposed to act as an antiseptic? I find a lot of recipes that suggest the addition of salt when preparing the ...
7k views

### Why can't a potassium sulfate anion KSO4(-) exist in solution?

Please explain to me why $\ce{KSO4^-}$ doesn't exist as a molecular ion in (aqueous) solution. I couldn't find a reason why. I assumed if you took one $\ce{SO4^{2-}}$ and one $\ce{K^+}$ ion, then ...
3k views

### Where does the characteristic peak for phtalic acid diethyl ester at m/z 149 originate?

Which fragmentation is possible at this m/z value for phthalic acid diethyl ester? I tried McLafferty but it didn't solve my problem.
136 views

### How can I reduce Crystallization temperature of seed oil to be used in winter as biodiesel?

How can I reduce Crystallisation temperature of seed oil to be used in winter as biodiesel? The glycerol has been removed from the oil, and white spirit is used to reduce its viscosity.
26k views

### Predicting the pH of a weak acid and weak base solution

I know that it is possible to predict whether combinations of acids and bases will be acidic, basic, or neutral: weak acid (WA) and strong base (SB) reacts basic strong acid (SA) and and weak base (...
23k views

### at constant volume why the change of enthalpy doesn't equal the change of heat

At constant pressure $p=\text{const.}$, change of internal energy equals heat subtract work(PV). So, $q=\Delta E - pV$. So is the the change of enthalpy. So we say at constant pressure, the change of ...
308 views

### Calculation of the enthalpy change of reactions

First, I’m a high school student and I wonder why every textbook just tells you how to set up those equations and cancel them to get the entropy change but never tells you why you can cancel the same ...