All Questions
Tagged with equilibrium physical-chemistry
434
questions
4
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1
answer
91
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Derivation of Gibbs phase rule
I learnt about the Gibbs phase rule a while back but did not really think too much about how it was derived. I am now currently looking back at the derivation provided in the textbook and I realised ...
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2
votes
0
answers
78
views
Does copper(II) hydroxide dissolve in ammonia solution?
According to University of Oregon — Chemistry Interactive Demonstrations and Educational Resources — Copper-Ammonia Complex, the equilibrium constant for the formation of copper(II) hydroxide is ...
- 620
0
votes
0
answers
74
views
If a pocket of nitrogen gas is pumped in at the bottom intake of a padded tank will the pocket of gas bubble up?
I have a nitrogen gas padded tank (tank 1) which is filled from the bottom of the tank. Tank has a set point of 30 psi which adjusted as tank level changes. Also at the inlet is an additional pipe ...
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3
votes
1
answer
113
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Effect of Pressure on the Position of Equilibrium
The following general reaction proceeds with decrease in amount of substance, so increasing pressure should shift the position of equilibrium to the right.
$$\ce{2 A(g) <=> B(g)}$$
But let's say ...
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3
votes
1
answer
65
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How can a Michaelis–Menten formalism be used when enzyme concentration isn't constant?
I understand that $V_\mathrm{max} = k_3[\ce{E}]_0$ in ordinary Michaelis–Menten (MM) kinetics. According to the lecture notes provided by my university (I don't believe they are available online), ...
- 31
0
votes
0
answers
32
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Understanding the relationship between Delta G and Kp, Kx and Kc
**Upon reading the chapter about equilibrium from my physical chemistry book, I was convinced that
ΔG=−RTln(Kp)(1)
and that
Kp=Kx(P∑v)(2)
where Kp
is the equilibrium constant with respect to pressure ...
- 11
-1
votes
3
answers
107
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How is it even possible that vapour pressure of liquid and vapour of solid are equal at freezing point? [duplicate]
My text book states The freezing point is defined as "the temperature at which the vapor pressure of the substance in its liquid phase is equal to its vapor pressure in the solid phase" Also ...
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-2
votes
1
answer
49
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Hydrolysis of $A_3B$ type weak acid-weak base salt
I know the formulae for weak acid-weak base salt of AB type. A peculiar question made me ask this. Do the formula for derived for AB type also hold for A3B type sal.
For example:
This is the question, ...
- 93
3
votes
0
answers
76
views
Bancroft's point
In the last problem (Problem 10.43) within the problem section of Chapter 10 in "Introduction to Chemical Engineering Thermodynamics" (J.M. Smith, H.C. Van Ness, M.M. Abbott, McGraw-Hill, ...
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-1
votes
1
answer
130
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Why is the ionic product of water also the equilibrium constant of dissociation of water?
This answer presents a derivation of the value of ionic product of water at $25^{\circ}\text{C}$.
The relation $K_\text{eq} = \operatorname{e}^{-\frac{\Delta_\text{r}G^{\circ}}{RT}}$ is used for the ...
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-3
votes
3
answers
109
views
How salt helps to melt ice even when there is no dynamic equilibrium between water and ice?
I am a high school student and I am confused about freezing point depression.
We say that when in winter's it gets even colder than normal freezing point Temperature then we use solute to melt ice ...
2
votes
2
answers
147
views
Boiling point, pressure, and Gibbs free energy
The water boiling process can be represented by the equation:
$$ \ce{H2O(l) → H2O(g)} \tag{1} $$
Since free energy depends on pressure
$$ \left(\frac{\partial G}{\partial P}\right)_T = V \tag{2} $$
...
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1
vote
1
answer
119
views
Does Hess' law in standard conditions involve consuming all reactants?
The standard free energy change for equilibrium problems is relative to both reactants AND products starting at 1 molar.
Hess’s law takes the sum of the values for products minus the sum of the values ...
- 21
5
votes
1
answer
162
views
Calculating partial pressure: Difficult cubic equation in bulky Chemical Equilibrium numerical
The problem, which I found in a popular book for Physical Chemistry, written by Neeraj Kumar, is fairly simple, being simply 2 equations and 2 variables, yet its simplification is a nightmare.
$\pu{5 ...
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0
votes
1
answer
63
views
Reaction kinetics exercise for hydrogen iodide synthesis
The rate constant for the reaction of hydrogen with iodine is $\pu{2.45E-4 M-1 s-1}$ at 302 °C and $\pu{0.905 M-1 s-1}$ at 508 °C.
a. calculate the activation energy and Arrhenius preexponential ...
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-4
votes
1
answer
87
views
What happens to the ions after dissociation in an aqueous solution? [closed]
I'm in high school studying about Buffer Solutions. We had an example of a solution made up of Ammonium Hydroxide and Ammonium Chloride for a Basic Buffer.
NH4OH ⇌ NH4 (+) + OH(-)
NH4Cl ⇌ NH4 (+) + ...
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1
vote
2
answers
184
views
How to obtain the expression for residual Gibbs energy?
The property involved is Gibbs free energy, the equations that I wrote are presented in my text book Introduction to chemical engineering thermodynamics by Smith and Van Ness, Chapter 6.
The thing is ...
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0
votes
1
answer
70
views
Can an electrode run out of the active species?
I have a background in solid state physics but am new to electrochemistry. I have been following the example of a physical chemistry (Mortimer) book that looks an electrochemical cell with a hydrogen ...
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-3
votes
1
answer
241
views
If Qc> Kc how can forward reaction can take place
If Qc>Kc then there will be a net backward reaction but still forward reaction will take place. My problem is if Qc>Kc forward reaction will become non spontaneous right. So how can that happen, ...
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-3
votes
1
answer
131
views
What if kc=1 will reactants concentration equals to product concentration [closed]
I read a book, it says if kc=1 it mean reactant concentration equals to product concentration at equilibrium. But I'm wondering that in kc expression we dont just use concentration of an element we ...
- 13
2
votes
3
answers
336
views
Change of equilibrium constant with respect to temperature
Suppose we have an arbitrary chemical reaction $A+B\rightleftharpoons 2C+D$ and its equilibrium constant at two temperatures $T_{1},T_{2}$ are $k_{1},k_{2}$. We can relate them as
$$\log\frac{k_{2}}{...
- 169
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votes
1
answer
84
views
Do complexes of a metal distribute in between the water and an organic compound layer?
My original question is one that is stated in the title, and I also have some side questions too.
I came across this question where you have a CuSO4 aqueous solution. Then you take an Ammonia aqueous ...
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1
vote
0
answers
254
views
How to calculate pH of a 0.1 M solution of ammonium bicarbonate considering simultaneous equilibrium along with hydrolysis?
We need to calculate the $\ce{[H+]}$ of 0.1M $\ce{(NH4+)(HCO3^-)}$ given the $\ce{k_b(NH4OH), k_{a_1}(H2CO3), k_{a_2}(HCO3^-)}$
The hint tells me to directly use the result $\ce{[H+]=\sqrt{k_{a_1}(\...
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4
votes
3
answers
1k
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What is the basis for the relationship of Gibbs energy and extent of reaction shown in this graph?
How this graph of Gibbs free energy between reaction coordinate is made because because
∆G = ∆G° + RT ln Q
and since ∆G° and T is constant hence the graph should be like that of ln(x)?
Source: https:/...
- 143
0
votes
4
answers
174
views
Which way Le Chatelier's principle
I have been pondering about the effect of pressure change in regard to Le Chatelier's principle on reactions. For this, I considered the following reaction:
$$\ce{CO(g) + 3H2(g) <=> CH4(g) + H2O(...
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0
votes
1
answer
120
views
Why change of gibbs energy per mole is zero at equilibrium?
I was reviewing this concept and thought of this: $\frac{dG}{dt} = \frac{\partial G}{\partial \xi}\frac{d \xi}{d t}$, for a reaction to be at equilibrium $\frac{d G}{d t}$ must be zero but I have ...
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1
vote
0
answers
94
views
Unit of equilibrium constant in formula for Gibbs free energy change at arbitrary temperature
We know the relation for Gibbs free energy change of a reaction at any stage and any temperature
$$\Delta G=\Delta G^{\circ}+RT\ln Q$$
where Q is reaction quotient. Subsequently, we get the rate ...
- 169
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votes
0
answers
105
views
Confusion about equilibrium constant in simultaneous equilibrium
Ok, so the equilibrium constant in terms of pressure is the ratio of partial pressures at equilibrium of gaseous products to reactants (all raised to the powers equal to the stoichiometric ...
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0
votes
3
answers
153
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Doubt in heterogenous equilibria [closed]
Let us take the following equilibrium:
$$\ce{NH4HS(s) <=> NH3(g) + H2S(g)}$$
I have been taught that since $\ce{NH4HS}$ is in the solid state, its concentration cant be taken and hence we write $...
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-1
votes
1
answer
373
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Why do we take active mass of water 1 but while calculating pKa of water as 55.345? [duplicate]
First, I should mention that the question was already asked here:Why is active mass of a pure solid or liquid always taken as unity?
But while calculating $\mathrm{p}K_\mathrm{a}$ of pure water we ...
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