Question

$K _{ u }$ values for acids $H _{2} SO _{3}, HNO _{2}, CH _{3} COOH$ and $HCN$ are respectively $1.3 \times 10^{-2}, 4 \times 10^{-4}, 1.8 \times 10^{-5}$ and $4 \times 10^{-10}$, which of the above acids produces stronger conjugate base in aqueous solution?

• A. $H_2SO_3$
• B. $HNO_2$
• C. $CH_3COOH$
• D. $HCN$

Answer 1

Answer: (D)

$HCN$

Answer 2

$K _{ a }( HCN )=4 \times 10^{-10}$
$HCN \rightleftharpoons H ^{+}+ CN ^{-}$
Weaker the acid, stronger the conjugate base.