Question

Identify conjugate acid and conjugate base for \(\mathrm{HCO_3^-}\) ion respectively.

• A. \(\mathrm{CO_3^{2-}}\) and \(\mathrm{H_2CO_3}\)
• B. \(\mathrm{H_2CO_3}\) and \(\mathrm{CO_3^{2-}}\)
• C. \(\mathrm{CO_2}\) and \(\mathrm{H_2CO_3}\)
• D. \(\mathrm{H_2CO_3}\) and \(\mathrm{CO^-}\)

Hint:

Remember: \[ \text{Conjugate Acid} = \text{Add } H^+ \] \[ \text{Conjugate Base} = \text{Remove } H^+ \] This shortcut works for all Brønsted acids and bases.

Answer 1

The Correct Option is B

Concept: According to Brønsted–Lowry theory:
• A conjugate acid is formed by addition of a proton (\(H^+\)).
• A conjugate base is formed by removal of a proton (\(H^+\)).

Step 1: Finding the conjugate acid of \(\mathrm{HCO_3^-}\).
Add one proton: \[ \mathrm{HCO_3^- + H^+ \rightarrow H_2CO_3} \] Thus, the conjugate acid is: \[ \mathrm{H_2CO_3} \]

Step 2: Finding the conjugate base of \(\mathrm{HCO_3^-}\).
Remove one proton: \[ \mathrm{HCO_3^- \rightarrow CO_3^{2-}+H^+} \] Thus, the conjugate base is: \[ \mathrm{CO_3^{2-}} \] Therefore, the correct answer is: \[ \boxed{(B)\ \mathrm{H_2CO_3\ and\ CO_3^{2-}}} \]