`Ph-NO_(2) overset(Sn//HCl)rarr underset("HCl, " 0^(@)C-5^(@)C)overset(NaNO_(2))rarr underset(Ph-OH)overset("Basic medium")rarr "Product Y"`
Find the molecular weight of Y report your answer as `underset(2)overset("Molecular weight")rarr`

Answer

To solve the problem, we need to follow the sequence of reactions step by step and determine the final product (Y) and its molecular weight.

### Step 1: Identify the starting compound
The starting compound is **Ph-NO₂** (Nitrobenzene). The molecular structure can be represented as:
- **C₆H₅-NO₂**

### Step 2: First reaction with Sn and HCl
The first reaction involves the reduction of nitrobenzene (Ph-NO₂) using tin (Sn) and hydrochloric acid (HCl). This reaction converts the nitro group (-NO₂) into an amino group (-NH₂), resulting in:
- **Ph-NH₂** (Aniline)

### Step 3: Second reaction with NaNO₂ in HCl at low temperature
The aniline (Ph-NH₂) then reacts with sodium nitrite (NaNO₂) in hydrochloric acid (HCl) at low temperatures. This reaction forms a diazonium salt:
- **Ph-N₂⁺Cl⁻** (Benzene diazonium chloride)

### Step 4: Third reaction with phenol in basic medium
Next, the diazonium salt reacts with phenol (C₆H₅-OH) in a basic medium. The -OH group of phenol replaces the diazonium group, leading to the formation of:
- **Ph-O-N=N-Ph** (P-hydroxy azo benzene)

### Step 5: Determine the molecular formula of Product Y
The molecular formula of P-hydroxy azo benzene can be derived as follows:
- The structure consists of:
- 12 Carbon (C) atoms
- 10 Hydrogen (H) atoms
- 2 Nitrogen (N) atoms
- 1 Oxygen (O) atom

Thus, the molecular formula is **C₁₂H₁₀N₂O**.

### Step 6: Calculate the molecular weight of Product Y
Now we calculate the molecular weight using the atomic weights:
- Carbon (C): 12 g/mol
- Hydrogen (H): 1 g/mol
- Nitrogen (N): 14 g/mol
- Oxygen (O): 16 g/mol

Now, we can calculate the total molecular weight:
- Molecular weight = (Number of C × Atomic weight of C) + (Number of H × Atomic weight of H) + (Number of N × Atomic weight of N) + (Number of O × Atomic weight of O)

Calculating:
- C: 12 × 12 = 144
- H: 10 × 1 = 10
- N: 2 × 14 = 28
- O: 1 × 16 = 16

Total molecular weight = 144 + 10 + 28 + 16 = **198 g/mol**

### Final Answer
Thus, the molecular weight of Product Y is:
\[ \underset{2}{\overset{\text{Molecular weight}}{\rightarrow}} 198 \]