The dissociation constants for acetic acid and HCN at 25^ ^ C are 1.5 × 10^ -5 and 4.5 × 10^ -10 , respectively. The equilibrium constant for the equilibrium - CN^ - +CH _ 3 COOH leftharpoons HCN+CH _ 3 COO^ - would be :

Correct answer: A. 3.0 × 10^4 aligned K_ c & =K_ a(CH_3 COOH) × 1 K_ a(HCN) & =1.5 ×10^ -5 × 1 4.5 × 10^ -10 & 3 ×10^4 aligned

NEET 2009

NEET 2009 · Chemistry · Thermodynamics (C)

The dissociation constants for acetic acid and HCN at 25^ ^ C are...

The dissociation constants for acetic acid and

\mathrm{HCN}

25^{{}^{\circ}} \mathrm{C}

are

1.5 \times 10^{-5}

and

4.5 \times 10^{-10}

, respectively. The equilibrium constant for the equilibrium -

\mathrm{CN}^{-}+\mathrm{CH}}_{3} \mathrm{COOH} \rightleftharpoons \mathrm{HCN}+\mathrm{CH}

}_{3}

\mathrm{COO}^{-}

would be :

A. $3.0 \times 10^4$

\begin{aligned}\mathrm{K}_{\mathrm{c}}& =\mathrm{K}_{\mathrm{a}\left(\mathrm{CH}_3 \mathrm{COOH}\right)} \times \frac{1}{\mathrm{ K}_{\mathrm{a}(\mathrm{HCN})}}\\ & =1.5 \times10^{-5} \times \frac{1}{4.5 \times 10^{-10}}\\ & \cong 3 \times10^4 \end{aligned}