In the following reaction `HC_2O_4^(-) (aq)+PO_4^(3-) (aq) hArr HPO_4^(2-)(aq)+C_2O_4^(2-)(aq)`, which are the two Bronsted bases ?

Options

A. `HC_2O^- and PO_4^(3-)`
B. `HPO_4^(2-) and C_2O_4^(2-)`
C. `HC_2O_4^(-) and HPO_4^(2-)`
D. `PO_4^(3-) and C_2O_4^(2-)`

Answer

To determine the two Brønsted bases in the reaction

\[ HC_2O_4^{-} (aq) + PO_4^{3-} (aq) \rightleftharpoons HPO_4^{2-} (aq) + C_2O_4^{2-} (aq), \]

we need to identify which species are acting as proton acceptors (Brønsted bases) in this equilibrium.

### Step-by-Step Solution:

1. **Identify the Reactants and Products**:
The reactants are \( HC_2O_4^{-} \) (the hydrogen oxalate ion) and \( PO_4^{3-} \) (the phosphate ion). The products are \( HPO_4^{2-} \) (the hydrogen phosphate ion) and \( C_2O_4^{2-} \) (the oxalate ion).

2. **Understand Brønsted Acid-Base Theory**:
According to Brønsted theory, an acid is a proton donor, while a base is a proton acceptor.

3. **Analyze the Reaction**:
- In the reaction, \( HC_2O_4^{-} \) donates a proton (H⁺) to \( PO_4^{3-} \).
- This means \( HC_2O_4^{-} \) is acting as an acid.
- The \( PO_4^{3-} \) accepts the proton and becomes \( HPO_4^{2-} \). Therefore, \( PO_4^{3-} \) is acting as a Brønsted base.

4. **Identify the Conjugate Bases**:
- After the reaction, \( C_2O_4^{2-} \) is formed from \( HC_2O_4^{-} \) after it donates a proton.
- Thus, \( C_2O_4^{2-} \) is the conjugate base of \( HC_2O_4^{-} \).

5. **Conclusion**:
The two Brønsted bases in the reaction are:
- \( PO_4^{3-} \) (which accepts a proton)
- \( C_2O_4^{2-} \) (which is the conjugate base of the acid \( HC_2O_4^{-} \))

### Final Answer:
The two Brønsted bases are \( PO_4^{3-} \) and \( C_2O_4^{2-} \).