Question

The degree of dissociation of acetic acid $(0.1mol.L^{-1})$ in water $(K_a$ of acetic acid is ${10}^{-5})$ is:

• A. $0.01$
• B. $0.5$
• C. $0.1$
• D. $1.0$

Answer 1

The correct option is A $0.01$

For weak acid,

$\alpha =(\frac{K_a}{C}{)}^{\frac{1}{2}}$

Here,

$\alpha$ is degree of dissociation

$K_a$ is dissociation constant which is given as ${10}^{-5}$

$C$ is concentration of acid which is given as $0.1mol{L}^{-1}$

On substituion of above values in the formula

$\alpha =(\frac{{10}^{-5}}{0.1}{)}^{\frac{1}{2}}$

$\alpha =({10}^{-4}){}^{\frac{1}{2}}$

$\alpha ={10}^{\frac{-4}{2}}$

$\alpha ={10}^{-2}$

$\alpha =0.01$

So the degree of dissociation of acetic acid is $0.01$.

Hence option $A$ is correct.