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KCET · Chemistry · Ionic Equilibrium

Conjugate base of \(\mathrm{H}_{2} \mathrm{PO}_{4}^{-}\)is

  1. A \(\mathrm{HPO}_{4}^{-}\)
  2. B \(\mathrm{HPO}_{4}^{2-}\)
  3. C \(\mathrm{H}_{3} \mathrm{PO}_{4}\)
  4. D \(\mathrm{PO}_{4}^{3-}\)
Verified Solution

Answer & Solution

Correct Answer

(B) \(\mathrm{HPO}_{4}^{2-}\)

Step-by-step Solution

Detailed explanation

A conjugate pair of acid and a base differs by a proton only, i.e.,
conjugate acid \(\rightleftharpoons\) conjugate base \(+\mathrm{H}^{+}\)
\(\mathrm{H}_{2} \mathrm{PO}_{4}^{-} \rightleftharpoons \mathrm{HPO}_{4}^{2-}+\mathrm{H}^{+}\)
Thus, \(\mathrm{H}_{2} \mathrm{PO}_{4}^{-}\)can give a proton and hence is an acid while \(\mathrm{HPO}_{4}^{2-}\) can accept the proton and hence is a base.