Question

Concentration CN- in 0.1 M HCN is [K 4x 101]

Answer 1

Answer: Option (c) is correct.

Explanation:

Concentration of HCN used = 0.1 M

the expression of $K_A$ is given as:

$HCN\rightarrow H^++CN^-$

According to reaction 1 mole of HCN will break down into 1 mol of $CN^-&H^+$

$K_a=4\times 10^{-10}=\frac{[H^+][CN^-]}{[HCN]}=\frac{x\times x}{0.1 M}$

$x=0.63\times 10^{-5} M = 6.3\times 10^{-6} M$

Hence, the correct answer is option (c).