Question

What will be the conjugate base of ${\mathrm{OH}}^{-}$ from the following?

• A. ${\mathrm{O}}^{2-}$
• B. ${\mathrm{H}}_2\mathrm{O}$
• C. ${\mathrm{O}}^{-}$
• D. ${\mathrm{O}}_2$

Answer 1

The correct option is A

${\mathrm{O}}^{2-}$

Explanation for the correct option:

(A) ${\mathrm{O}}^{2-}$

• A conjugate base is a part of acid which is left after removing ${\mathrm{H}}^{+}$from it.
• If ${\mathrm{H}}^{+}$ion is removed from ${\mathrm{OH}}^{-}$, the remaining part obtained is ${\mathrm{O}}^{2-}$.

${\mathrm{OH}}^{-}\to {\mathrm{O}}^{2-}+{\mathrm{H}}^{+}$

• Thus, the conjugate base of ${\mathrm{OH}}^{-}$ is ${\mathrm{O}}^{2-}$.

Explanation for the incorrect options:

(B) ${\mathrm{H}}_2\mathrm{O}$

• This is obtained when ${\mathrm{H}}^{+}$is added to ${\mathrm{OH}}^{-}$.
• Thus, it is not a conjugate base of ${\mathrm{OH}}^{-}$.

(C) ${\mathrm{O}}^{-}$

• This is not obtained when ${\mathrm{H}}^{+}$ion is removed from ${\mathrm{OH}}^{-}$.
• Thus, it is not a conjugate base of ${\mathrm{OH}}^{-}$.

(D) ${\mathrm{O}}_2$

• This is not obtained when ${\mathrm{H}}^{+}$ion is removed from ${\mathrm{OH}}^{-}$.
• Thus, it is not a conjugate base of ${\mathrm{OH}}^{-}$.

Hence, option (A) is correct. The conjugate base of ${\mathrm{OH}}^{-}$ is ${\mathrm{O}}^{2-}$.