In salts of polyatomic anion, as polarising power of cation increase, thermal stability of the salt decrease and decomposed species may further undergo redox reaction
Q. Which of the followinng species undergoes non-redox thermal decomposition reaction on heating?

Options

A. `FeSO_(4)`
B. `SnSO_(4)`
C. `H_(2)C_(2)O_(4)`
D. `Na_(2)HPO_(4)`

Explanation

To solve the question regarding which species undergoes a non-redox thermal decomposition reaction upon heating, we will analyze the provided options step by step.

### Step 1: Understand Non-Redox Reactions
A non-redox reaction is one in which there is no change in the oxidation states of the elements involved. This means that no electrons are gained or lost during the reaction.

### Step 2: Analyze Each Option
We will examine the thermal decomposition of each compound provided in the options to determine if they undergo redox reactions or not.

#### Option 1: FeSO4 (Iron(II) sulfate)
- **Decomposition Reaction**:
\[ \text{FeSO}_4 \rightarrow \text{Fe}_2\text{O}_3 + \text{SO}_2 + \text{SO}_3 \]
- **Oxidation States**:
- Fe in FeSO4: +2
- Fe in Fe2O3: +3
- S in SO4: +6
- S in SO2: +4
- S in SO3: +6
- **Conclusion**: There is a change in oxidation states (Fe is oxidized from +2 to +3, and S is reduced). Therefore, this is a redox reaction.

#### Option 2: SnSO4 (Tin(II) sulfate)
- **Decomposition Reaction**:
\[ \text{SnSO}_4 \rightarrow \text{SnO}_2 + \text{SO}_2 \]
- **Oxidation States**:
- Sn in SnSO4: +2
- Sn in SnO2: +4
- S in SO4: +6
- S in SO2: +4
- **Conclusion**: There is a change in oxidation states (Sn is oxidized from +2 to +4, and S is reduced). Therefore, this is also a redox reaction.

#### Option 3: H2C2O4 (Oxalic acid)
- **Decomposition Reaction**:
\[ \text{H}_2\text{C}_2\text{O}_4 \rightarrow \text{CO} + \text{CO}_2 + \text{H}_2\text{O} \]
- **Oxidation States**:
- C in H2C2O4: +3
- C in CO: +2
- C in CO2: +4
- **Conclusion**: There is a change in oxidation states (C is oxidized from +3 to +4 and reduced from +3 to +2). Therefore, this is a redox reaction.

#### Option 4: Na2HPO4 (Sodium hydrogen phosphate)
- **Decomposition Reaction**:
\[ \text{Na}_2\text{HPO}_4 \rightarrow \text{Na}_4\text{P}_2\text{O}_7 + \text{H}_2\text{O} \]
- **Oxidation States**:
- Na: +1 (remains +1)
- H: +1 (remains +1)
- P in HPO4: +5 (remains +5)
- **Conclusion**: There are no changes in oxidation states for any of the elements. Therefore, this is a non-redox reaction.

### Final Answer
The species that undergoes a non-redox thermal decomposition reaction on heating is **Na2HPO4**.