Statement 1: An aqueous solution of ammonium cyanide is basic. Statement 2: For a salt of a weak acid and a weak base, pH = 7 + 2 1 ( p K a − p K b ) , so the nature of the solution depends on t

Question

Statement 1: An aqueous solution of ammonium cyanide is basic.

Statement 2: For a salt of a weak acid and a weak base, $pH = 7 + \frac{1}{2} (p K_{a} - p K_{b})$ , so the nature of the solution depends on the relative values of $K_{a}$ and $K_{b}$ .

(Given $K_{a}$ of HCN $= 4.9 \times 1 0^{- 10}$ , $K_{b}$ of $NH_{3} = 1.8 \times 1 0^{- 5}$ .)

TestHub · Accepted Answer

p K a ​ ( HCN ) = 9.31 and p K b ​ ( NH 3 ​ ) = 4.74 . pH = 7 + 0.5 × ( 9.31 − 4.74 ) = 9.3 , so the solution is basic: Statement 1 is true. Statement 2 is a true statement and is exactly why the pH exceeds 7 here. Answer: (A).

Chemistry - Ionic Equilibrium Question with Solution | TestHub

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