Which of the following statements is not correct

Options

A. `FeSO_(4)` solution is used for purification of NO
B. `NH_(4)NO_(3) ` gives `N_(2)O` on heating
C. `PbNO_(3)` gives paramagnetic, brown coloured gas on thermal decomposition.
D. `PCl_(5)` act as an oxidising agent not reducing agent.

Explanation

To determine which of the statements is not correct, we will analyze each statement one by one.

### Step 1: Analyze the First Statement
**Statement:** "FeSO4 solution is used for purification of NO."

**Analysis:** This statement is incorrect. FeSO4 (iron(II) sulfate) is not used for the purification of nitric oxide (NO); rather, it is used to absorb NO. When FeSO4 interacts with NO, it forms a brown-colored complex, FeSO4·NO. Therefore, this statement is false.

### Step 2: Analyze the Second Statement
**Statement:** "When ammonium nitrate is heated, it gives N2O and water."

**Analysis:** This statement is correct. When ammonium nitrate (NH4NO3) is heated, it decomposes to produce nitrogen gas (N2) and water (H2O). The balanced reaction can be represented as:
\[ 2 NH4NO3 \rightarrow N2 + 2 H2O + O2 \]
Thus, this statement is true.

### Step 3: Analyze the Third Statement
**Statement:** "Lead nitrate gives a paramagnetic brown-colored gas on thermal decomposition."

**Analysis:** This statement is also correct. When lead(II) nitrate (Pb(NO3)2) is thermally decomposed, it produces nitrogen dioxide (NO2), which is a brown gas and is paramagnetic due to the presence of unpaired electrons. The reaction can be represented as:
\[ 2 Pb(NO3)2 \rightarrow 2 PbO + 4 NO2 + O2 \]
Thus, this statement is true.

### Step 4: Analyze the Fourth Statement
**Statement:** "PCl5 acts as an oxidizing agent, not a reducing agent."

**Analysis:** This statement is correct. In PCl5, phosphorus is in the +5 oxidation state. It cannot act as a reducing agent because it cannot be oxidized further (it cannot exceed the +5 oxidation state). However, it can act as an oxidizing agent as it can be reduced to a lower oxidation state (such as +3). Therefore, this statement is true.

### Conclusion
After analyzing all the statements, the only incorrect statement is the first one regarding FeSO4 and its use in the purification of NO.

**Final Answer:** The incorrect statement is the first one: "FeSO4 solution is used for purification of NO."

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