Question

The dissociation constant on n-butyric acid is $1.6\times {10}^{-5}$ and the molar conductivity at infinite dilution is $380\times {10}^{-4}$ $S{m}^{2}mo{l}^{-1}.$ The specific conductance of the 0.01 M acid solution is:

• A. $1.52\times {10}^{-5}S{m}^{-1}$
• B. $1.52\times {10}^{-2}S{m}^{-1}$
• C. $1.52\times {10}^{-3}S{m}^{-1}$
• D. None

Answer 1

Answer: (B)

$1.52\times {10}^{-2}S{m}^{-1}$

Given: $K_a=1.6\times {10}^{-5}$, $C=0.01M$, ${\Lambda }_m^{\infty }=380\times {10}^{-4}S{m}^{2}mo{l}^{-1}$

specific conductance: $\kappa ={\Lambda }_m^{\infty }\times C_{eq}\times 1000$

Equilibrium concentration of acid: $C_{eq}=\sqrt{K_a\times C}{C}_{eq}=4\times {10}^{-4}mol/L\kappa =380\times {10}^{-4}\times 4\times {10}^{-4}\times 1000\kappa =1.52\times {10}^{-2}S/m$

Hence, option $B$ is correct.