Consider the following sequence of reactions :

Molar mass of the product formed (A) is ______$$gmol^{-1}$$.

We need to determine the molar mass of the final product (A) formed in the given reaction sequence starting from nitrobenzene.

Reaction Sequence Analysis:

• Step 1: Reduction ($$\text{Sn} + \text{HCl}$$)
  Nitrobenzene is reduced to aniline ($$\text{C}_6\text{H}_5\text{NH}_2$$).
• Step 2: Diazotization ($$\text{NaNO}_2 + \text{HCl, } 0^\circ\text{C}$$)
  Aniline reacts to form benzene diazonium chloride ($$\text{C}_6\text{H}_5\text{N}_2^+\text{Cl}^-$$).
• Step 3: Sandmeyer Reaction ($$\text{Cu}_2\text{Cl}_2$$)
  The diazonium group is replaced by chlorine, yielding chlorobenzene ($$\text{C}_6\text{H}_5\text{Cl}$$).
• Step 4: Wurtz-Fittig / Fittig Reaction ($$\text{Na / dry ether}$$)
  Two molecules of chlorobenzene couple together in the presence of sodium metal to form biphenyl as the final product (A).

Molar Mass Calculation of Product (A):

• The molecular formula of biphenyl is $$\text{C}_{12}\text{H}_{10}$$.
• Atomic masses: $$\text{C} = 12\text{ g/mol}$$, $$\text{H} = 1\text{ g/mol}$$.
• $$\text{Molar Mass} = (12 \times 12) + (10 \times 1)$$
  $$\text{Molar Mass} = 144 + 10 = 154\text{ g/mol}$$

Answer: 154