Question

0.2 M solution of formic acid is ionized 3.2$\%$, its ionization constant is

• A. $9.6\times {10}^{-3}$
• B. $2.1\times {10}^{-4}$
• C. $1.25\times {10}^{-6}$
• D. $4.8\times {10}^{-5}$

Answer 1

The correct option is B $2.1\times {10}^{-4}$

$K_a=C{\alpha }^2$
$=0.2\times {\left(\frac{3.2}{100}\right)}^2=2.048\times {10}^{-4}=2.1\times {10}^{-4}$