Question

Calculate the ratio of $HCO{O}^{-}$ and $F^{-}$ in a mixture of $0.2MHCOOH(K_a=2\times {10}^{-4})$ and $0.1MHF(K_a=6.6\times {10}^{-4})$.

• A. $1:6.6$
• B. $1:3.3$
• C. $2:3.3$
• D. $3.3:2$

Answer 1

The correct option is C $2:3.3$

For a solution of two monoprotic acid,
${\alpha }_1/{\alpha }_2=K_1/K_2$
So, ratio is $\frac{0.2\times 2\times {10}^{-4}}{6.6\times 0.1\times {10}^{-4}}=2:3.33$