Identify the total number of atoms in product Q in the given sequence of reaction `C_(6)H_(5)NH_(2)overset(NaNO_(2)+HCl)rarr Xoverset(Cu_(2)(CN)_(2))rarr Yoverset(H_(2)O //H^(+))rarrZoverset(NaOH//CaO,Delta)rarrPoverset(Cl_(2)hv"(Excess)")rarrQ`

Answer

To identify the total number of atoms in product Q from the given sequence of reactions, we will follow the steps outlined in the reaction sequence.

### Step-by-Step Solution:

1. **Identify the Starting Compound:**
The starting compound is aniline, represented as \( C_6H_5NH_2 \). This molecule consists of:
- 6 Carbon (C) atoms
- 5 Hydrogen (H) atoms
- 1 Nitrogen (N) atom
- Total: 6 + 5 + 1 = 12 atoms

2. **Formation of Diazonium Salt:**
When aniline reacts with sodium nitrite (\( NaNO_2 \)) and hydrochloric acid (\( HCl \)), it forms a diazonium salt. The structure of the diazonium salt can be represented as \( C_6H_5N_2^+Cl^- \). In this compound:
- 6 Carbon (C) atoms
- 5 Hydrogen (H) atoms
- 2 Nitrogen (N) atoms
- 1 Chlorine (Cl) atom
- Total: 6 + 5 + 2 + 1 = 14 atoms

3. **Hydrolysis of Diazonium Salt:**
The diazonium salt undergoes hydrolysis to form phenol (\( C_6H_5OH \)). In phenol:
- 6 Carbon (C) atoms
- 5 Hydrogen (H) atoms
- 1 Oxygen (O) atom
- Total: 6 + 5 + 1 = 12 atoms

4. **Decarboxylation with Soda Lime:**
The phenol is then treated with soda lime (\( NaOH \) and \( CaO \)), which leads to decarboxylation. However, in this case, phenol does not have a carboxyl group to remove, so it remains as phenol:
- Total remains: 12 atoms

5. **Chlorination of Benzene:**
The phenol is then chlorinated using chlorine (\( Cl_2 \)) in the presence of UV light. This reaction introduces chlorine atoms into the benzene ring, resulting in hexachlorobenzene (\( C_6Cl_6 \)). In hexachlorobenzene:
- 6 Carbon (C) atoms
- 6 Chlorine (Cl) atoms
- Total: 6 + 6 = 12 atoms

6. **Final Count of Atoms in Product Q:**
The final product Q, which is hexachlorobenzene, contains:
- 6 Carbon (C) atoms
- 6 Chlorine (Cl) atoms
- Total: 6 + 6 = 12 atoms

### Conclusion:
The total number of atoms in product Q is **12 atoms**.