The study of chemical systems using the laws and concepts of physics. This usually requires the techniques of thermodynamics, statistical mechanics and quantum mechanics.
0
votes
1answer
28 views
How to calculate mole fraction of each element in an ionic compound? [closed]
A solution is prepared by dissolving 518g of K2SO4 in a small amount f water and diluted it with water to a volume of 2.5L(calculate the mole fraction of water,K+,SO4-2)
I got that the mole fraction ...
0
votes
0answers
29 views
How to calculate molarity,molality, vapor pressure, freezing point, boiling point? [closed]
A solution is prepared in a cold room(4.0 C) by dissolving 118g of potassium nitrate(KNO3) in 750 mL of water. The resulting solution had a volume 745 mL.
Calculate the molarity of the resulting ...
2
votes
3answers
38 views
On the scale of stuff with a pH
I am a confused (and somewhat anal retentive) non-chemist who is trying to understand what pH is. I have come to understand it is a measure of acidity, but I have not yet figured out what that means ...
0
votes
0answers
27 views
I need the mathematical equations that represent the absorption of CO2 in a column
I want to mathematically model a carbon dioxide absorption column using the equilibrium model (not rate based or dynamic) but I am having trouble finding the same number of numerical equations as I ...
0
votes
0answers
13 views
Reverse Rates in SSH Theory
I am currently implementing V-V transitions for $N_2$ in a code I work with. For now, I am only using Schwartz-Slawsky-Herzfeld Theory for this, and will move on to more accurate/sophisticated ...
0
votes
0answers
19 views
Butane Burning Color
Why does Butane burn blue? From my (very) basic understanding of chemistry, carbon and hydrogen do not burn blue, their radiation spectra are different-so why should the combination burn blue?
Please ...
0
votes
1answer
33 views
How do I know if concentration of Ammonia affected my absorbency measurements?
This is for determination of copper in a penny Lab. After making standard solutions we made a solution with a penny, dissolving it in nitric acid and adding ammonium hydroxide to form a more ...
0
votes
2answers
64 views
Lewis model and modern physics
Electron affinity of chlorine = -349 kJ per mole. And, first ionization energy of sodium = 496 kJ per mole while energy required for combining= 147 kJ per mole.
Isn't it a contradiction against ...
-1
votes
2answers
74 views
What are the main axis of research in Chemistry? [closed]
I would like to know what are the main problems currently studied in Chemistry.
For some reason, it seems that there is far less vulgarisation in chemistry than the other fields, and it's hard to ...
2
votes
1answer
55 views
$K_c$ expression for heterogeneous equilibrium
Consider this reaction. :-
$CaCO_3(s) \rightleftharpoons CaO(s) + CO_2(g)$
for this, Kc=[ $CO_2$ g)]
For a given temperature, Kc will remain fixed. That means, the amount of $CO_2$ released ...
0
votes
0answers
13 views
Piezoluminent compound on football skin for glow
Which piezoluminance chemical compound can be used on football so that it can be seen in dark as well?
Like on beaches, medows, etc at evening.
2
votes
2answers
55 views
Equilibrium constant
I know that equilibrium constant depends on temperature and pressure. But according to Le Chatelier's principle when we change pressure of reagents the equilibrium is the same. Why?
1
vote
1answer
38 views
Why do aqueous solutions always have to be electrically neutral?
I was reviewing some analytical chemistry and stumbled upon a section that explained the imperfection of using a salt bridge.
It said that the using dissimilar ions is a problem because in, for ...
0
votes
0answers
13 views
parrallel reaction
Consider a substance $\ce{A}$ that forms a mixture of $\ce{P1}$ and $\ce{P2}$ in parallel reactions, with
$k_1 = 1.40\times10^{-3} \text{ s}^{-1}$ and $k_2 = 8.7 \times 10^{-3} \text{ s}^{-1}$. In an ...
1
vote
1answer
24 views
Are there any free electrons in metal vapor?
Metals contain free moving electrons, in both the solid and liquid state. Does this happen when it is in vapor form?
1
vote
1answer
64 views
I have to write a Python program relating with molecular weight. Any insight?
I have a program assignment here, and I was wondering if anyone can point me in the right direction as to where to start and how to approach problems like this.
Write a program that determines the ...
0
votes
1answer
70 views
Reactions of Sodium Halides with Sulphuric acid
$$\ce{NaF +H_2SO_4 \rightarrow NaHSO_4 +HF} (1a)$$
$$\ce{NaCl +H_2SO_4 \rightarrow NaHSO_4 +HCl} (1b)$$
$$\ce{2NaBr +H_2SO_4 + 2H^+ \rightarrow Br_2 +SO_2 + 2H_2O + 2Na^+} (2)$$
$$\ce{8NaI +H_2SO_4 ...
3
votes
1answer
39 views
Removing wine stains from a decanter
I have a decanter which I use fairly often to pour out wines. I typically rinse it with hot water after the last wine has come out, but I cannot prevent it from forming 'residual' wine stains over ...
0
votes
2answers
206 views
When is it okay to use $Q=mc\Delta T$, is this equation only for calorimetry questions?
When is it okay to use $Q=mc\Delta T$, is the equation only for calorimetry questions? When a question talks about heat how do I know if i'm measuring $\Delta H$ or Q?
3
votes
2answers
73 views
Did Mendeleev predict the existence of neutrinos?
According to this Wikipedia page, Mendeleev originally believed that the inert gases belonged in Group 0 (to the left of the alkali metals). Thus, helium would be placed in the second period to the ...
0
votes
1answer
53 views
Electrochemical Cell
Now in an electrochemical cell , we make use of the fact that whenever there is a potential drop , electrons will flow from lower to higher potential as for a potential drop , there must be an ...
1
vote
2answers
80 views
What are the factors behind making ice faster?
Recently I saw a video in YouTube about how to make ice in seconds.
In this video, salt is added to a glass of water and then a straw is closed from one end and the other side is lit using a lighter ...
1
vote
1answer
47 views
Why do transition elements make colored compounds?
Why do transition metals element make colored compound both in solid form and in solution? Is it related with their electrons or something else?
0
votes
0answers
27 views
What should I study for my ACS final? [closed]
My Chemistry I class in college is having the final be the ACS standard chemistry test I guess. I was wondering what I need to study for that test. Are there any online helps or practice tests?
0
votes
0answers
40 views
Salt Hydrolysis
Referring to this, when "hydrolysis of a salt" is its reaction with water:
How is it that both the cation and anion of the salt are reacting in an equal amount with water?
To state this specifically ...
2
votes
3answers
59 views
Balancing a chemical equation
I'm in chemistry and I still have a hard time comprehending how to balance a chemical equation.
What are the main steps and general things to know?
thank you.
0
votes
0answers
31 views
Polar group strong dipole effect molecular axis
There are some fundamental charactaristics of liquid crystal. One of them is that all liquid crystals are organic compounds and at one side of their long molecular foundation there exists a polar ...
1
vote
1answer
27 views
What determines a substance's energy of activation with air?
Ice will melt when heat is applied; paper will catch fire. In trying to figure out why — what the difference is between things that melt and things that catch — I found "Burn, Char, Melt" by Roberto ...
0
votes
1answer
41 views
Application of the Arrhenius equation to a parallel reaction
I'm struggling with this homework question:
"For a parallel reaction A goes to B with rate constant $k_1$ and A goes to C with rate constant $k_2$, you determine that the activation energies are 71.9 ...
0
votes
1answer
44 views
Why does the melting point get lower going down the Alkali Metal Group with increase in atomic number?
Why does the melting point get lower going down the Alkali Metal Group with increase in atomic number?
-1
votes
1answer
46 views
which chemical element has the lowest boiling point? [closed]
which chemical element has the lowest boiling point?
Is it Helium(He) or is it Hydrogen(H)?
Hydrogen is lighter than Helium.
0
votes
1answer
51 views
Standard electrode potential of a galvanic half cell is zero at equilibrium at standard conditions?
At standard conditions(at 1atm pressure and unit activity(1molal or 1molar concentration)of all dissolved compounds),the electrode potential is equal to the standard electrode potential by the Nernst ...
4
votes
1answer
40 views
What does under-stoichiometric or stoichiometric mean?
When people talk about oxides like $\ce{SiO2}$ or $\ce{Al2O3}$, they use expressions like stoichiometric or under-stoichiometric. I understand that this refers to the relative composition of ...
0
votes
3answers
52 views
How does Caesium's density change with temperature?
According to Wikipedia Caesium's density is 1,90 g/cm3 at T=20 °C. How does this change when T changes? E.g. will it expand when melting?
0
votes
2answers
40 views
How to find the molecular weight of a given gas?
It's given that the density of a gas(X) is 10 times that of hydrogen. In that case, what is the molecular weight of gas X?
Well what I've done up to now is this:
...
1
vote
0answers
48 views
In an acid, what does $\ce{ClO_3-}$ reduce into?
...but, most importantly, why? It's $$\ce{6e- +ClO_{3}^- +6H^+ \rightarrow Cl^- + 3 H_2O}$$
Now, with the gift of foresight, why was the equation for its oxidation not instead $$\ce {2e^- +ClO_{3}^- ...
1
vote
1answer
53 views
Solid hydrophilic transparant materials that don't dissolve in water
I am looking for hydrophilic transparant materials which are solid at room temperature and that don't dissolve in water. I need these for an experiment in which I condense droplets on a plate made out ...
5
votes
2answers
96 views
Measuring Thermodynamic Stability
We can predict whether a reaction can occur spontaneously by calculating the change in Gibbs' free energy.
I was just wondering whether there is any general measure of the thermodynamic stability of ...
1
vote
1answer
39 views
How was the quantum 3-Body problem solved?
What method was used to solve the quantum 3-Body Problem? I heard it was solved and was not sure about the status of the problem.
2
votes
1answer
108 views
Why are intramolecular Hydrogen bonds weaker than intermolecular hydrogen bonds?
Why are intramolecular Hydrogen bonds weaker than intermolecular hydrogen bonds ?
The question is itself in the main topic.
Thanks in advance... :)
0
votes
3answers
89 views
Carbon atoms in triple bonds
I was trying to know what is the probability for the carbon atoms to rotate .I know that in single bond it is 0 % and I think it is 100 % in double bond but how about the triple bond ?
1
vote
1answer
108 views
Question regarding mole concept
5.5 g of a mixture of $\ce{FeSO4.7H2O}$ and $\ce{Fe2(SO4)3.9H2O}$ requires $5.4 \:\mathrm{mL}$ of $0.1 \:\mathrm{N}$ $\ce{KMnO4}$ solution for complete oxidation. Calculate the number of moles of ...
3
votes
1answer
48 views
$K_{eq} $ vs $K_c$
I was wondering if there was a difference between $K_{eq}$ and $K_c$. I think they both refer to the Equilibrium Constant. If I'm wrong, could you please tell me the difference between the two? ...
2
votes
1answer
50 views
Boiling and Melting point of Lithium (or any other element that does not occure in free state)
The melting and boiling point of Lithium as compared to other members of the Alkali group metals is high. But, Lithium does not occur in the free state.
So, what does it mean that it has high ...
1
vote
3answers
98 views
Why can't we use fusion to make ourselves rich?
As we know on fusing two hydrogen atoms we can convert it to helium and by breaking them we get two $\ce{H}$ atoms. So why can't we convert mercury to gold by removing 1 proton per atom?
2
votes
2answers
66 views
What reactions will their reaction rates increase with time?
My textbook states that for most reactions, the reaction rate decreases with time. I wonder what reactions will have increasing reaction rates with time. I know that adding a catalyst will increase ...
0
votes
1answer
45 views
Unsure how to find the activity, once I found the activity coefficient
Ok, this is a simple problem, but I cant see how to get the answer. I calculated the activity coefficient, $\gamma_\pm$ = 0.389, and I need to find the activity $a_\pm$ for a 0.0120m solution of ...
4
votes
2answers
143 views
Bonding and anti-bonding orbitals in the light of time-dependent Schrödinger equation?
In organic chemistry, people draw 2p orbitals like this:
and then they explain how the orbitals combine to non-bonding (π*) or bonding (π) molecular orbitals, like this:
depending on whether the ...
2
votes
1answer
56 views
Why can sulphur act like a catalyst?
In the reaction of combustion of gunpowder,
Sulfur is used to speed up the reaction and acts like a catalyst in that it increases the rate of reaction. However, unlike a catalyst, it is used up in ...
1
vote
1answer
32 views
The colour of fireworks
When the electrons that are excited by the energy of burning drop back into lower energy levels they emit light at the wavelength of colour.
When metals are burnt, metal oxides(some coloured) are ...
