Question

Is it possible for a reaction to have a large equilibrium constant but small forward and reverse rate constants?

Answer 1

The equilibrium constant K and the forward rate constant k1 and backward rate constant k2 has the following relation:

K = k1 / k2

 

So from the equation, we can say that yes it is possible to have large K even if k1 is small given that k2 is very small compared to k1: (k2 very less than 1)

k2 << k1

Answer 2

The condition which makes the equilibrium constant very large with the smaller value of the forward and backward rate constant is,

$\boxed{{{\mathbf{k}}_{\mathbf{f}}}{\mathbf{>>}}{{\mathbf{k}}_{\mathbf{b}}}}$

Further explanation:

Equilibrium constant:

The equilibrium constant is expressed as the equilibrium concentration of products divided by the equilibrium concentration of reactants raised to power of their stoichiometric coefficient in the balanced chemical equation.

For the given general reaction,

${\text{aA + bB}}\to{\text{cC + dD}}$

The expression for equilibrium constant is,

$K=\frac{{{{\left[{\text{C}}\right]}^{\text{c}}}{{\left[{\text{D}}\right]}^{\text{d}}}}}{{{{\left[{\text{A}}\right]}^{\text{a}}}{{\left[{\text{B}}\right]}^{\text{b}}}}}$

Here K is equilibrium constant of the reaction.

Another definition:

The equilibrium reaction consists the forward reaction and reverse reaction and both reaction have their respective rate constant, therefore, equilibrium constant can also be defined as the ratio of rate constant of forward reaction to the rate constant of backward reaction.

$K=\frac{{{k_{\text{f}}}}}{{{k_{\text{b}}}}}$

Here, ${k_{\text{f}}}$ is rate constant of forward reaction and ${k_{\text{b}}}$ is rate constant of backward reaction.

In the given case equilibrium constant should be larger with smaller values of rate constants. Therefore, the rate constants of backward reaction must be very small from the rate constant of backward reaction so that the value of the ratio is very large.

Hence the condition which makes the equilibrium constant very large with the smaller value of forward and backward rate constant is,

${{\mathbf{k}}_{\mathbf{f}}}{\mathbf{>>}}{{\mathbf{k}}_{\mathbf{b}}}$

Learn more:

1. Calculation of equilibrium constant of pure water at 25°c: brainly.com/question/3467841

2. Complete equation for the dissociation of na2co3(aq): brainly.com/question/5425813

Answer details:

Grade: Senior school

Subject: Chemistry

Chapter: Equilibrium

Keywords: Equilibrium, reactions, reverse reaction, forward reaction, backward reaction, rate constant, reverse rate constant, forward rate constant, larger value of equilibrium constant, kf>kb.