Question 13.1: Writing Equilibrium Equations for Gas-Phase Reactions Write ......
Writing Equilibrium Equations for Gas-Phase Reactions
Write the equilibrium equation for each of the following reactions:
(a) N_2(g) + 3 H_2(g) \rightleftharpoons 2 NH_3(g)
(b) 2 NH_3(g) \rightleftharpoons N_2(g) + 3 H_2(g)
STRATEGY
Put the concentrations of the reaction products in the numerator of the equilibrium-constant expression and the concentrations of the reactants in the denominator. Then raise the concentration of each substance to the power of its coefficient in the balanced chemical equation.
(b) K_{\mathrm{c}}{ }^{\prime}=\frac{\left[\mathrm{N}_2\right]\left[\mathrm{H}_2\right]^{3 \ \leftarrow \ Coefficient \ of \ H_2}}{\left[\mathrm{NH}_3\right]^{2 \ \leftarrow \ Coefficient \ of \ NH_3}} \ \ \ \ \ \ \ \ K_c{ }^{\prime}=\frac{1}{K_c}
Because the balanced equation in part (b) is the reverse of that in part (a), the equilibrium-constant expression in part (b) is the reciprocal of the expression in part (a) and the equilibrium constant K_{c}^{ʹ} is the reciprocal of K_c