Question

What will be the ionisation constant of formic acid if its $0.01M$ solution is $14.5\%$ ionised?

• A. $2.1\times 10^{-4}$
• B. $14.5$
• C. $0.145$
• D. $1.45\times 10^{-4}$

Answer 1

Answer: (A)

$K_a=c{\alpha }^2$
$\alpha =\frac{14.5}{100}=0.15$
$K_a=0.01\times {\left(0.145\right)}^2$
$=2.1\times 10^{-4}$