Question

construct the expression for ka for the weak acid, hcn. hcn(aq) + h₂o(l) ⇌ h₃o⁺(aq) + cn⁻(aq) based on the definition of ka, drag the tiles into the numerator or denominator to construct the expression for the given acid. ka =

Explanation:

Step1: Recall the formula for \(K_a\)

For a weak acid \(HA\) (in this case \(HCN\)) with the dissociation reaction \(HA + H_2O
ightleftharpoons H_3O^++A^-\), the acid - dissociation constant \(K_a=\frac{[H_3O^+][A^-]}{[HA]}\).

Step2: Identify the species in the \(HCN\) dissociation reaction

In the reaction \(HCN(aq)+H_2O(l)
ightleftharpoons H_3O^+(aq)+CN^-(aq)\), \(HA = HCN\), \(H_3O^+\) is the hydronium ion, and \(A^-=CN^-\).

Answer:

\(\frac{[H_3O^+][CN^-]}{[HCN]}\)