What is the equilibrium constant expression (K_a)for the acid dissociation of hydrocyanic acid HCN? The equation of interest is HCN(aq)+ H₂O(l)⇌ H₃O⁺(aq)+ CN^-(aq). A)K_a = ([H₃O⁺][CN^-])/([HCN][H₂O]) B)K_a = ([H₃O⁺][CN^-])/([HCN]) C)K_a = ([HCN][H₂O])/([H₃O⁺][CN^-]) D)K_a = ([HCN])/([H₃O⁺][CN^-])

Question

Quizplus · Accepted Answer

The equilibrium constant expression for the dissociation of an acid in water does not include the concentration of water (H2O) because it is a pure liquid and its concentration is considered constant and thus not included in the expression. Therefore, the correct expression is the concentration of the products divided by the concentration of the reactant, excluding water.

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

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