Question

Write the expressions for the equilibrium constants of the reactions below.

Answer 1

In general, for a given chemical reaction in equilibrium

$aA + bB \rightleftharpoons cC + dD$

the equilibrium constant, Keq, will be

$K_{eq}=\frac{\mathrm{[C]^c}[D]^d}{\mathrm{[A]^a[B]^b}}.$

Usually, only aqueous and gaseous species are included in the equilibrium constant; the concentration of any pure solid or liquid is omitted. While the states of the reactants and products in the reactions for this problem aren't given, these three particular reactions all happen to be ones where they can (and, in fact, do) occur where all the species are in the gaseous state. So, all the reactants and product(s) are included in the equilibrium constants below, but this will not always be the case.

a.

$K_{eq}=\frac{\mathrm{[NH_3]^2}}{\mathrm{[N_2][H_2]^3}}$

b.

$K_{eq}=\frac{\mathrm{[HBr]^2}}{\mathrm{[Br][H_2]}}$

c.

$K_{eq}=\frac{\mathrm{[H_2][CO_2}]}{\mathrm{[CO][H_2O]}}$