The conjugate base of HCO_3^ - is:A) {H_2}C{O_3}B) CO_3^{2 - }C) C{O_2}D) {H_2}O

To determine the conjugate base of \( \text{HCO}_3^- \), we need to understand the concept of conjugate acids and bases.

In general:
- An acid's conjugate base is what remains after the acid donates a proton (H\(^+\)).
- Conversely, a base's conjugate acid is what is formed when the base accepts a proton (H\(^+\)).

Let's apply this to \( \text{HCO}_3^- \):

1. **Identify \( \text{HCO}_3^- \) as an acid or base:** \( \text{HCO}_3^- \) (bicarbonate ion) can act as a weak acid. When it donates a proton (H\(^+\)), it forms its conjugate base.

2. **Determine the conjugate base:** When \( \text{HCO}_3^- \) loses a proton (H\(^+\)), it becomes \( \text{CO}_3^{2-} \) (carbonate ion).

So, the conjugate base of \( \text{HCO}_3^- \) is \( \text{CO}_3^{2-} \).

The correct answer is: **B) \( \text{CO}_3^{2-} \)**.