Question

Four species are listed below.
$\left(i\right)HC{O}_3^{-}$
$\left(ii\right)H_3{O}^{+}$
$\left(iii\right)HS{O}_4^{-}$
$\left(iv\right)HS{O}_{3}F$
Which one of the following is the correct sequence of their acid strength?

• A. $\left(iii\right)<\left(i\right)<\left(iv\right)<\left(ii\right)$
• B. $\left(iv\right)<\left(ii\right)<\left(iii\right)<\left(i\right)$
• C. $\left(ii\right)<\left(iii\right)<\left(i\right)<\left(iv\right)$
• D. $\left(i\right)<\left(iii\right)<\left(ii\right)<\left(iv\right)$

Answer 1

The correct option is D $\left(i\right)<\left(iii\right)<\left(ii\right)<\left(iv\right)$

The order of acidic strength is
$HC{O}_3^{-}<HS{O}_4^{-}<H_3{O}^{+}<HS{O}_{3}F$
$HS{O}_{3}F$ is super acid and it is the most acidic among them. $H_3{O}^{+}$ is more acidic than anions because anions $(HC{O}_3^{-},HS{O}_4^{-})$ do not release $H^{+}$ ion easily. $HS{O}_4^{-}$ is more acidic than $HC{O}_3^{-}$ because sulphur is more electronegative than carbon.