A 0.250 L aqueous solution contains a total cyanide-species concentration,

CHEMISTRY · Subjective · A Level · Chemistry · Acids and bases · Acids and bases

Problem

[\text{HCN}] + [\text{CN}^{−}]

, of 0.250 M and has a measured pH of 9.31 at 25 °C. For the equilibrium HCN(aq) ⇌ H

^{+}

(aq) + CN

^{-}

(aq)

K_a = 4.9 \times 10^{-10}

at this temperature. Calculate the equilibrium concentration of HCN(aq) (in mol L

^{-1}