Question

The equilibrium constant for the given reaction is approximately 10^–3

$HPO_{4}^{2 -}$ (aq) + $\mathrm { HCO } _ { 3 } ^ { - }$(aq) $\rightleftarrows$

$\mathrm { H } _ { 2 } \mathrm { PO } _ { 4 } ^ { - }$(aq) + (aq)

Which is strongest conjugate base in the given reaction ?

• A. $HPO_{4}^{2 -}$ (aq)
• B. $HCO_{3}^{-}$ (aq)
• C. $H_{2}PO_{4}^{-}$ (aq)
• D. $CO_{3}^{2 -}$ (aq)

Answer 1

Answer: (D)

$CO_{3}^{2 -}$ (aq)

Answer 2

$CO_{3}^{2 -}$ + $H_{2}PO_{4}^{-}$ $\rightleftarrows$ $HPO_{4}^{2 -}$ + $HCO_{3}^{2 -}$ K_c = 10³

Therefore $CO_{3}^{2 -}$ is the stronger conjugate base than $HPO_{4}^{2 -}$