All Questions
Tagged with equilibrium kinetics
19
questions
33
votes
4
answers
69k
views
Why are solids and liquids not included in the equilibrium constant? What about in a reaction rate calculation?
Take for instance the reaction
$$\ce{H2(g) + I2(s) <=> 2HI(g)}$$
The equilibrium constant would not include the solid $\ce{I2}$, but why is this? I have read that its concentration is a ...
- 3,256
13
votes
3
answers
7k
views
How is it that the equilibrium constant does not depend on the mechanism?
For a reaction of the form
$$\ce{aA + bB <=> cC + dD}$$
the equilibrium constant is
$$K_c=\frac{[\ce{C}]^c[\ce{D}]^d}{[\ce{A}]^a[\ce{B}]^b}$$
regardless of the mechanism of the reaction. ...
- 1,201
26
votes
4
answers
4k
views
Relation between chemical kinetics and chemical equilibrium
In my chemistry book, the law of chemical equilibrium is derived from the law of mass action:
For a reversible chemical reaction $$\ce{aA +bB\rightleftharpoons cC + dD}$$ where $a$, $b$, $c$ and $d$ ...
- 5,685
20
votes
1
answer
619
views
Can a multi-species system oscillate around equilibrium?
In reading about chemical oscillations such as those that occur in the Belousov–Zhabotinsky reaction (BZ), it's often reported that these reactions were initially not taken seriously, because of a ...
- 1,661
19
votes
2
answers
30k
views
Is there a difference between equilibrium and steady state?
The term equilibrium is used in the context of reversible reactions that reach a point where concentrations no longer change. The term steady-state is used in enzyme kinetics when the concentration of ...
- 41.2k
0
votes
2
answers
2k
views
Why is the rate of a reaction proportional to the concentrations of reactants raised to their stoichiometric coefficients?
Consider a gaseous state elementary reaction $$\ce{aA(g) + bB(g)} \overset{k_\mathrm{f}}{\underset{k_{\mathrm{b}}}{\ce{<=>}}}\ce{ cC(g) + dD(g)}$$
I know that for this reaction, $$\Delta G = \...
- 1,278
21
votes
4
answers
27k
views
Why are equilibrium constants unitless?
I haven’t quite reached the point where I can read a full-fledged text on chemical kinetics and thermodynamics yet, so bear with me, please.
I’m wondering why a value like $K_\text{eq} = \frac{[\ce{...
- 831
9
votes
3
answers
935
views
Why is the equilibrium constant defined that way intuitively?
Suppose we have chemical equation: $$\ce{ aA + bB <=> cC + dD }$$
then equilibrium constant is defined: $$K=\frac{[C]^c[D]^d}{[A]^a[B]^b}$$
but why don't we define it as: $$K=\frac{cd[C][D]...
- 199
4
votes
1
answer
1k
views
Formation of hydrogen bromide: Does the concept of "order" apply to this reaction?
Started reading Levine's Physical Chemistry [1] yesterday, and I hit upon (another) wall.
On page 517, Chapter 15, she includes a reaction resulting in the formation of $\ce{HBr}$ from $\ce{H2}$ and $\...
- 18.8k
4
votes
1
answer
1k
views
Equilibrium constant for heterogeneous equilibria having aqueous as well as gaseous reactants
Suppose we have a heterogenous equilibrium :
$$\ce{A(aq) +B(aq) <=> C(g) +D(aq)}$$
Which equilibrium constant is used here?
Both pressure and concentration terms are there. So, according to me, ...
- 487
2
votes
4
answers
4k
views
Le Chatelier's principle: what are the effects of decreasing volume?
Which of the following is increased by decreasing the volume of the
reaction system in the following reaction: $\ce{2H_2S(g) +3O_2(g)<=>
2SO_2(g) +2H_2O(g)} + {\text{heat}}$
I. Rate of ...
- 1,796
1
vote
2
answers
604
views
Which rate, the forward or reverse rate of acid dissociation, is more strongly affected when diluting acetic acid in aqueous solution?
Acetic acid is a weak acid. It is in equilibrium with acetate and hydronium ions in aqueous solution:
$$\ce{CH3COOH(aq) + H2O(l) <=> CH3COO-(aq) + H3O+(aq)}$$
Ostwald's law states that the ...
- 41.2k
8
votes
4
answers
833
views
Deriving kinetic equations for reversible reactions
Problem
Given the reaction $\ce{A <=>[$k_\mathrm f$][$k_\mathrm b$] B}$ with rate constants $k_\mathrm f = \pu{4E-2 s-1}$ and $k_\mathrm b = \pu{10^{-2} s-1}$. Initially, $\pu{2 mol}$ of $\ce{A}...
- 1,817
3
votes
2
answers
1k
views
Why does a dynamic equilibrium exist?
We know that at equilibrium Gibbs free energy is minimum. We also know that at equilibrium both forward and reverse reactions occur simultaneously, and we also know that for a reaction to be ...
- 3,487
3
votes
4
answers
19k
views
At equilibrium are the rates of the forward and backward reactions equal to zero?
At equilibrium, the concentrations do not change with time. So, is it true that the rates of the chemical reactions are zero at equilibrium? Wikipedia says that they are not zero. Why is this?
