Question

The degree of ionization of $0.10\, M$ lactic acid is $4.0 \%$

The value of $K_{c}$ is

• A. $1.66 \times 10^{-5}$
• B. $1.66 \times 10^{-4}$
• C. $1.66 \times 10^{-3}$
• D. $1.66 \times 10^{-2}$

Answer 1

Answer: (B)

$\%$ dissociation $=4 \%$

degree of dissociation $(\alpha)=\frac{4}{100}=0.04$

For lactic acid



$\therefore K_{c} =\frac{C \alpha \cdot C \alpha}{C(1-\alpha)} =\frac{C \alpha^{2}}{(1-\alpha)}$

$=\frac{0.1 \times 0.04 \times 0.04}{(1-0.04)}$

$=\frac{1.6 \times 10^{-4}}{0.96}=1.66 \times 10^{-4}$