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NEET levelSingle correct optionDifficulty 1 of 3ia002

An aqueous solution of sodium cyanide, $NaCN$ , has a pH greater than 7 because

A $Na X^{+}$ is hydrolysed to give $OH X^{-}$
B $CN X^{-}$ is the conjugate base of a strong acid
C $CN X^{-}$ is the conjugate base of the weak acid HCN and accepts a proton from water
D $NaCN$ ionises to give free $OH X^{-}$ directly

Answer: C

Na X^{+}

comes from a strong base and does not hydrolyse. HCN is a weak acid, so

CN X^{-}

is a fairly strong base:

CN X^{-} + H X_{2} O HCN + OH X^{-}

. The excess

OH X^{-}

makes the solution basic.

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