Hydrocyanic acid, HCN, is a weak acid. Which of the following is the correct expression for the K_a of hydrocyanic acid? A) [H₃O⁺][HCN]/[CN-] B) [H₃O⁺][CN-]/[HCN] C) [HCN]/[ H₃O⁺][CN-] D) [HCN][CN-]/[ H₃O⁺]

Question

Quizplus · Accepted Answer

K_a is the acid dissociation constant for the reaction HCN + H2O ⇌ H3O+ + CN-. The expression for K_a is [H₃O⁺][CN-]/[HCN], which matches option B.

Hydrocyanic Acid, HCN, Is a Weak Acid