All Questions
Tagged with equilibrium physical-chemistry
434
questions
1
vote
1
answer
480
views
Acid dissociation constant calculated from the ionization percentage
The question goes like this:
An acid (HX) is 25% dissociated in water. If the equilibrium concentration of HX is $\pu{0.30 M}$, calculate the value of $K_\mathrm{a}$.
So I tried as follows:
if I ...
3
votes
0
answers
187
views
Why is it that when dG°<0, dH°<0? [closed]
Let me preface this question by saying that I probably made a mistake somewhere. However, I can't figure out what it is.
I was messing around with the Gibbs free energy equation to determine how the ...
- 360
1
vote
0
answers
97
views
Density and partial pressure [closed]
A sample of $\ce{NOBr}$ gas was placed in a rigid flask where it decomposes at $\pu{25 ^\circ C}$ according to the following reaction:
$$\ce{2NOBr(g) <=> 2NO(g) + Br2(g)}$$
At equilibrium, the ...
2
votes
1
answer
318
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Relation between standard silver-silver chloride electrode potential and solubility product of silver chloride
I learned that $E^\circ_\ce{Cl^-|Ag,AgCl}, E^\circ_\ce{Ag^+|Ag}$ and $K_\mathrm{sp}$ of $\ce{AgCl}$ are related as
$$\boxed{E^\circ_\ce{Cl^-|Ag,AgCl} = E^\circ_\ce{Ag^+|Ag} + \frac{RT}{F}\ln K_\mathrm{...
- 750
0
votes
1
answer
506
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What's the equilibrium pressure of CO2 gas over sodium hydroxide?
Many (too many) decades ago in physical chemistry lessons, I seem to recall that given the enthalpy changes of reactions, and maybe phase diagrams, one could work out what equilibrium a reaction would ...
- 141
1
vote
1
answer
127
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Finding solubility of salts of polyprotic acids
Problem
Given, for $\ce{H3PO4}$,
$\mathrm{pK_\mathrm{a_1}=2.2}$
$\mathrm{pK_\mathrm{a_2}=7.2}$
$\mathrm{pK_\mathrm{a_3}=12.4}$
For the salt $\ce{Mg(NH4)PO4}$, $\mathrm{pK_\mathrm{sp}=12.6}$ and the ...
- 1,817
2
votes
1
answer
225
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Intuition for relation between electrode potential and reaction quotient
Consider the following reaction in a galvanic cell: $$\ce{X(s) + Y+(aq) -> Y(s) + X+(aq)}$$
According to the Nernst equation, $$E =E_\circ - \dfrac{RT}{F}\ln\left(\dfrac{\ce{[X+]}} {\ce{[Y+] }} \...
- 750
1
vote
1
answer
221
views
Why is "activity" of gaseous component equal to its partial pressure but that of aqueous component its concentration?
While solving an electrochemistry problem I had to calculate the reaction quotient of this reaction:
$$\ce{2Fe(s) + 4H+(aq) + O2(g) -> 2Fe^{2+} (aq) + 2H2O (l)}$$
It turns out to be: $$\ce{Q=\dfrac{...
- 750
3
votes
0
answers
174
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Why aren't electrons included in the equilibrium constant expression?
This might be elementary, but why aren't electrons included in the equilibrium constant for a half-reaction?
For example, for
$$\ce{O2 (g) + 4H+ (aq) + 4e- -> 2H2O(l)}$$
we have
$$Q = \frac{(a_\ce{...
- 1,241
2
votes
1
answer
205
views
Can we have an equilibrium constant for a reaction at constant volume?
Suppose we have a sealed container (fixed volume) and we introduce two gases $\ce{A}$ and $\ce{B}$. The two reactants
$$\ce{A + B <=> C}$$
form another gas $\ce{C}$ with equilibrium constant $K$....
- 766
1
vote
1
answer
366
views
Calculating pH of aqueous ammonium hydrogen sulfide solution
I was doing the following question yesterday:
Calculate the pH of a $\pu{0.1 M}$ solution of $\ce{NH4HS}$, given $\mathrm{p}K_\mathrm{b}$ of $\ce{NH3}$ is $4.74$, and $\mathrm{p}K_\mathrm{a1}$ and $\...
- 1,411
5
votes
1
answer
2k
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Does pressure affect pH? [closed]
Since pH is the function of $\ce{H+}$ ion concentration, the change in volume will change the equilibrium according to Le Chatelier's principle and affect the pH. Is it correct, or are there any ...
- 73
5
votes
0
answers
38
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Do the differential expressions of second law of thermodynamics imply a smooth increase in entropy? [closed]
Another statement of second law of thermodynamics can be formulated in terms of system properties and not properties + surroundings (isolated system). For a closed system at constant temperature and ...
- 766
6
votes
1
answer
773
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Can the equilbrium constant ever be exactly 1?
According to my book,
In the real world [...] it is unlikely that any reaction would have exactly equal concentrations of products and reactants at equilibrium.
This was mentioned in context to the ...
- 155
4
votes
0
answers
84
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Regarding Ellingham diagrams
In my textbook, the following information is given about Ellingham diagram:
The interpretation of $\ce{\Delta_rG^\circ}$ is based on ${K}$ ($\ce{\Delta G^\circ = -RTlnK}$). Thus it is presumed that ...
- 549