Which of the following consitute a set of amphoteric species?
(a). `H_(2)O,H_(2)PO_(3)^(Theta), HPO_(4)^(2-)`
(b). `HC_(2)O_(4)^(Theta),H_(2)PO_(4)^(Theta),SO_(4)^(2-)`
(c). `H_(2)O,HPO_(4)^(2-),H_(2)PO_(2)^(Theta)`
(d). `H_(3)O^(o+),H_(2)PO_(4)^(Theta),HCO_(3)^(Theta)`

Options

A. `H_(3)O^(+), H_(2)PO_(4)^(-), HCO_(3)^(-)`
B. `H_(2)O, HPO_(4)^(2-),H_(2)PO_(2)^(-)`
C. `H_(2)O, H_(2)PO_(4)^(-), HPO_(4)^(2-)`
D. `HC_(2)O_(4)^(-), H_(2)PO_(4)^(-), SO_(4)^(2-)`

Answer

To determine which of the given options constitutes a set of amphoteric species, we first need to understand the definition of amphoteric species. Amphoteric species are substances that can both donate a proton (act as an acid) and accept a proton (act as a base).

Now, let's analyze each option step by step.

### Step 1: Analyze Option (a) `H2O, H2PO3^(Theta), HPO4^(2-)`
- **H2O**: Water can act as both an acid (donating H+) and a base (accepting H+). So, it is amphoteric.
- **H2PO3^(Theta)**: This species can also donate and accept protons, thus it is amphoteric.
- **HPO4^(2-)**: This species can also donate and accept protons, making it amphoteric.

**Conclusion for Option (a)**: All three species are amphoteric.

### Step 2: Analyze Option (b) `HC2O4^(Theta), H2PO4^(Theta), SO4^(2-)`
- **HC2O4^(Theta)**: This species can donate a proton to form C2O4^(2-), and it can accept a proton to form H2C2O4. Thus, it is amphoteric.
- **H2PO4^(Theta)**: This species can donate a proton to form HPO4^(2-) and accept a proton to form H3PO4. Thus, it is amphoteric.
- **SO4^(2-)**: This species cannot donate a proton (it has no H+ to lose) but can accept one to form HSO4^(-). Thus, it is not amphoteric.

**Conclusion for Option (b)**: Not all species are amphoteric (SO4^(2-) is not).

### Step 3: Analyze Option (c) `H2O, HPO4^(2-), H2PO2^(Theta)`
- **H2O**: As previously established, it is amphoteric.
- **HPO4^(2-)**: As previously established, it is amphoteric.
- **H2PO2^(Theta)**: This species can accept a proton to form H3PO2 but cannot lose a proton. Thus, it is not amphoteric.

**Conclusion for Option (c)**: Not all species are amphoteric (H2PO2^(Theta) is not).

### Step 4: Analyze Option (d) `H3O^(o+), H2PO4^(Theta), HCO3^(Theta)`
- **H3O^(o+)**: This species can donate a proton to form H2O but cannot accept a proton. Thus, it is not amphoteric.
- **H2PO4^(Theta)**: As previously established, it is amphoteric.
- **HCO3^(Theta)**: This species can donate a proton to form CO3^(2-) and accept a proton to form H2CO3. Thus, it is amphoteric.

**Conclusion for Option (d)**: Not all species are amphoteric (H3O^(o+) is not).

### Final Conclusion
After analyzing all the options, we find that only option (a) contains a complete set of amphoteric species.

**Correct Answer**: (a) `H2O, H2PO3^(Theta), HPO4^(2-)`

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