Question

Apply the law of mass action to the following equilibria: (i) formation of \(\mathrm{SO}_{3}\) from \(\mathrm{SO}_{2}\) and \(\mathrm{O}_{2}\) (ii) formation of \(\mathrm{NO}_{2}\) from nitric oxide and oxygen

Short answer

Question: Write the expressions for the equilibrium constants, \(K_c\), for the following reactions, using the law of mass action: (i) Formation of \(\mathrm{SO}_{3}\) from \(\mathrm{SO}_{2}\) and \(\mathrm{O}_{2}\) (ii) Formation of \(\mathrm{NO}_{2}\) from nitric oxide and oxygen Answer: (i) \(K_c = \frac{[\mathrm{SO}_{3}]^2}{[\mathrm{SO}_{2}]^2[\mathrm{O}_{2}]}\) (ii) \(K_c = \frac{[\mathrm{NO}_{2}]^2}{[\mathrm{NO}]^2[\mathrm{O}_{2}]}\)

Step-by-step solution

(i) Formation of \(\mathrm{SO}_{3}\) from \(\mathrm{SO}_{2}\) and \(\mathrm{O}_{2}\)

The balanced chemical equation for the formation of \(\mathrm{SO}_{3}\) from \(\mathrm{SO}_{2}\) and \(\mathrm{O}_{2}\) is: $$2\mathrm{SO}_{2}(g) + \mathrm{O}_{2}(g) \rightleftharpoons 2\mathrm{SO}_{3}(g)$$ Now we can write the expression for the equilibrium constant, \(K_c\), using the law of mass action as: $$K_c = \frac{[\mathrm{SO}_{3}]^2}{[\mathrm{SO}_{2}]^2[\mathrm{O}_{2}]}$$ Where [A] denotes the concentration of species A at equilibrium.

(ii) Formation of \(\mathrm{NO}_{2}\) from nitric oxide and oxygen

The balanced chemical equation for the formation of \(\mathrm{NO}_{2}\) from nitric oxide and oxygen is: $$2\mathrm{NO}(g) + \mathrm{O}_{2}(g) \rightleftharpoons 2\mathrm{NO}_{2}(g)$$ Now we can write the expression for the equilibrium constant, \(K_c\), using the law of mass action as: $$K_c = \frac{[\mathrm{NO}_{2}]^2}{[\mathrm{NO}]^2[\mathrm{O}_{2}]}$$ Where [A] denotes the concentration of species A at equilibrium.