Question

Conjugate acid and conjugate base of \( HCO_3^- \) are respectively

• A. \( H_2CO_3, H_3CO_3^+ \)
• B. \( H_2CO_3, CO_3^{2-} \)
• C. \( CO_3^{2-}, H_2CO_3 \)
• D. \( CO_3^{2-}, CO_2 \)

Hint:

To find the conjugate acid of a species, add a proton (\( H^+ \)) to it. To find the conjugate base of a species, remove a proton (\( H^+ \)) from it. Remember to adjust the charge accordingly.

Answer 1

The Correct Option is B

According to the Brønsted-Lowry acid-base theory, an acid is a proton (\( H^+ \)) donor, and a base is a proton acceptor.
A conjugate acid is formed when a base accepts a proton.
A conjugate base is formed when an acid donates a proton.
We are given the species \( HCO_3^- \).
To find its conjugate acid, we need to add a proton (\( H^+ \)) to it: $$ HCO_3^- + H^+ \rightarrow H_2CO_3 $$ So, the conjugate acid of \( HCO_3^- \) is \( H_2CO_3 \) (carbonic acid).
To find its conjugate base, we need to remove a proton (\( H^+ \)) from it: $$ HCO_3^- \rightarrow CO_3^{2-} + H^+ $$ So, the conjugate base of \( HCO_3^- \) is \( CO_3^{2-} \) (carbonate ion).
Therefore, the conjugate acid and conjugate base of \( HCO_3^- \) are \( H_2CO_3 \) and \( CO_3^{2-} \) respectively.
This corresponds to option (B).
Note that \( HCO_3^- \) can act as both an acid and a base (amphoteric species).