Answer:
Ka = [H⁺] × [CN⁻] / [HCN]
Step-by-step explanation:
Cyanhydric acid is a weak acid, according to the following equation:
HCN(aq) ⇄ H⁺(aq) + CN⁻(aq)
The acid ionization constant (Ka) is equal to the product of the concentrations of the ions raised to the stoichiometric coefficients divided by the concentration of the undissociated acid raised to its stoichiometric coefficient.
Ka for HCN is:
Ka = [H⁺] × [CN⁻] / [HCN]