Consider following reaction:
`Cl_(2)(g)+H_(2)O overset(R.T.)to P+Q`
If molecular weight of P is less than Q then incorrect statement is:

Options

A. On warming 'P' can form deep red coloured vapours with `CrO_(3)`
B. Q' exhibits bleaching property
C. `MnO_2` can change `P` into `Cl_(2)` gas on warming
D. P' reacts with `H_(2)S` gas while 'Q' does not

Explanation

To solve the problem, we need to analyze the reaction between chlorine gas (Cl₂) and water (H₂O) and identify the products formed, as well as their molecular weights. The reaction can be represented as:

\[ \text{Cl}_2(g) + \text{H}_2\text{O} \rightarrow P + Q \]

### Step 1: Identify the Products
When chlorine gas reacts with water, the products formed are hydrochloric acid (HCl) and hypochlorous acid (HOCl). Thus, we can assign:
- \( P = \text{HCl} \)
- \( Q = \text{HOCl} \)

### Step 2: Determine Molecular Weights
Next, we need to calculate the molecular weights of the products:
- Molecular weight of HCl:
- H: 1 g/mol
- Cl: 35.5 g/mol
- Total = 1 + 35.5 = 36.5 g/mol

- Molecular weight of HOCl:
- H: 1 g/mol
- O: 16 g/mol
- Cl: 35.5 g/mol
- Total = 1 + 16 + 35.5 = 52.5 g/mol

### Step 3: Compare Molecular Weights
From the calculations:
- Molecular weight of \( P \) (HCl) = 36.5 g/mol
- Molecular weight of \( Q \) (HOCl) = 52.5 g/mol

Since the molecular weight of \( P \) (HCl) is less than that of \( Q \) (HOCl), the statement "the molecular weight of P is less than Q" is true.

### Step 4: Evaluate the Statements
Now we evaluate the given statements to determine which one is incorrect:
1. **Option A**: "On warming, P can form deep red colored vapors with CrO₃." - This is correct as HCl can react with CrO₃ to produce chromium trichloride, which can produce deep red vapors.

2. **Option B**: "Q exhibits bleaching property." - This is correct because hypochlorous acid (HOCl) can release nascent oxygen, which is a bleaching agent.

3. **Option C**: "MnO₂ can change P into Cl₂ gas on warming." - This is also correct as MnO₂ can oxidize HCl to form Cl₂.

4. **Option D**: "P reacts with H₂S gas while Q does not." - This statement is incorrect. HCl does not react with H₂S, but HOCl does react with H₂S to form HCl, sulfur, and water.

### Conclusion
The incorrect statement is **Option D**.

---