Question

The conjugate base of ${\mathrm{H}}_3{\mathrm{BO}}_3$ is?

• A. ${{\mathrm{HBO}}_3}^{2-}$
• B. ${\mathrm{H}}_4{\mathrm{BO}}^{3+}$
• C. $\mathrm{B}{\left(\mathrm{OH}\right)}^{4-}$
• D. ${\mathrm{H}}_3{\mathrm{BO}}^{3-}$

Answer 1

The correct option is C

$\mathrm{B}{\left(\mathrm{OH}\right)}^{4-}$

The explanation for the correct option:

Option(C):$\mathrm{B}{\left(\mathrm{OH}\right)}^{4-}$

• According to the theory of Conjugate Acid-Base pair, acids are known as proton i.e ${\mathrm{H}}^{+}$ donors or acceptors of ${\mathrm{OH}}^{-}$ whereas bases are basically known as proton acceptors or donors of ${\mathrm{OH}}^{-}$.
• Hence, the conjugate base of a given acid is formed by either donating the ${\mathrm{H}}^{+}$ from the acid or accepting the ${\mathrm{OH}}^{-}$ ion from the respective conjugate base.
• Therefore, using the above concept, we can conclude that, the Conjugate base of ${\mathrm{H}}_3{\mathrm{BO}}_3$​ is $\mathrm{B}{\left(\mathrm{OH}\right)}^{4-}$, which can be given as:
  ${\mathrm{H}}_3{\mathrm{BO}}_3\left(\mathrm{aq}\right)+{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right)\to \mathrm{B}{\left(\mathrm{OH}\right)}^{4-}+{\mathrm{H}}^{+}$

The explanation for the incorrect option:

Option(A):${{\mathrm{HBO}}_3}^{2-}$

• The conjugate base of ${\mathrm{H}}_3{\mathrm{BO}}_3$ is not given as ${{\mathrm{HBO}}_3}^{2-}$.
• Hence, the given option is the incorrect one.

Option(B):${\mathrm{H}}_4{\mathrm{BO}}^{3+}$

• ${\mathrm{H}}_4{\mathrm{BO}}^{3+}$is not represented as the conjugate base of ${\mathrm{H}}_3{\mathrm{BO}}_3$.
• Thus the given option does not represent the correct concept.

Option(D):${\mathrm{H}}_3{\mathrm{BO}}^{3-}$

• The conjugate base of ${\mathrm{H}}_3{\mathrm{BO}}_3$ is not given as ${\mathrm{H}}_3{\mathrm{BO}}^{3-}$.
• Thus the given option does not coincide with the correct concept.

Hence, the conjugate base of ${\mathrm{H}}_3{\mathrm{BO}}_3$ is $\mathrm{B}{\left(\mathrm{OH}\right)}^{4-}$option (C) is the correct answer.