Problem 18 - Chemistry: The Central Science

Question

Which of the following reactions lies to the right, favoring the formation of products, and which lies to the left, favoring formation of reactants? (a) \(2 \mathrm{NO}(g)+\mathrm{O}_{2}(g) \rightleftharpoons 2 \mathrm{NO}_{2}(g) ; K_{p}=5.0 \times 10^{12}\) (b) \(2 \mathrm{HBr}(g) \rightleftharpoons \mathrm{H}_{2}(g)+\mathrm{Br}_{2}(g) ; K_{c}=5.8 \times 10^{-18}\)

Step-by-Step Solution

Answer

Reaction (a) lies to the right, favoring the formation of products, since \(K_p = 5.0 \times 10^{12}\) which is greater than 1. Reaction (b) lies to the left, favoring the formation of reactants, since \(K_c = 5.8 \times 10^{-18}\) which is less than 1.

Step 1: Reaction (a) Direction

For reaction (a), we have: \(2 \mathrm{NO}(g)+\mathrm{O}_{2}(g) \rightleftharpoons 2 \mathrm{NO}_{2}(g)\) The equilibrium constant Kp is given as: \(K_{p} = 5.0 \times 10^{12}\) Since the value of \(K_p\) is greater than 1, this means that the reaction favors the formation of products. Therefore, reaction (a) lies to the \(\boxed{right}\).

Step 2: Reaction (b) Direction

For reaction (b), we have: \(2 \mathrm{HBr}(g) \rightleftharpoons \mathrm{H}_{2}(g)+\mathrm{Br}_{2}(g)\) The equilibrium constant Kc is given as: \(K_{c} = 5.8 \times 10^{-18}\) Since the value of \(K_c\) is less than 1, this means that the reaction favors the formation of reactants. Therefore, reaction (b) lies to the \(\boxed{left}\).