For which of the following equilibria does Kc correspond to an acid-ionization constant, Ka? NH3(aq) + H3O+(aq) NH4+(aq) + H2O(l) NH4+(aq) + H2O(l) NH3(aq) + H3O+(aq) NH4+(aq) + OH-(aq) NH3(aq) + H2O(l) HF(aq) + OH-(aq) H2O(l) + F-(aq) F-(aq) + H2O(l) HF(aq) + OH-(aq)