If for at 25°C is 4.7, what is the pH of a 0.5 M aqueous solution? — Ionic Equilibrium Chemistry Question

💡 Solution & Explanation

$NaCN$ is a salt of WA-SB. $pK_b(CN^-) = 4.7 \implies pK_a(HCN) = 14 - 4.7 = 9.3$. Formula: $pH = 7 + \frac{1}{2}pK_a + \frac{1}{2}\log C = 7 + 4.65 + 0.5\log(0.5) = 11.65 - 0.15 = 11.5$.