What Is the Equilibrium Constant Expression (K_a)for the Acid Dissociation

Multiple Choice

What is the equilibrium constant expression (K_a) for the acid dissociation of nitrous acid HNO₂? The equation of interest is HNO₂(aq) + H₂O(l) ⇌ H₃O⁺(aq) + NO₂^-(aq) .

A) K_a = ([H₃O⁺][NO₂^-]) /([HNO₂][H₂O])
B) K_a = ([H₃O⁺][NO₂^-]) /([HNO₂])
C) K_a = ([HNO₂][H₂O]) /([H₃O⁺][NO₂^-])
D) K_a = ([HNO₂]) /([H₃O⁺][NO₂^-])