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

question 136

Multiple Choice

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^-])

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