The value of x is _________.

The reaction sequence is carried out in two distinct steps.

Step 1 : Formation of the inorganic salt
$$\mathrm{Sn + 2\,HCl \;\longrightarrow\; SnCl_2 + H_2}$$
1 mol of Sn gives 1 mol of $$\mathrm{SnCl_2}$$.

Step 2 : Reduction of nitrobenzene by the stannous chloride formed in Step 1
A commonly used, completely balanced equation for this reduction in an acid medium is
$$\mathrm{C_6H_5NO_2 + 3\,SnCl_2 + 6\,HCl \;\longrightarrow\; C_6H_5NH_3Cl + 3\,SnCl_4 + 2\,H_2O}$$ $$-(1)$$
From $$-(1)$$, 1 mol of nitrobenzene (or of the organic salt produced) consumes 3 mol of $$\mathrm{SnCl_2}$$.

Moles of the organic salt obtained
The product isolated is anilinium chloride, $$\mathrm{C_6H_5NH_3Cl}$$.
Its molar mass is
$$M = 6(12) + 8(1) + 14 + 35 = 129\;\text{g mol}^{-1}$$.

Given mass of the salt = 1.29 g, therefore
$$n\bigl(\mathrm{C_6H_5NH_3Cl}\bigr) = \frac{1.29}{129} = 0.01\;\text{mol}$$.

Moles of $$\mathrm{SnCl_2}$$ required
Using the 1 : 3 ratio from $$-(1)$$,
$$n\bigl(\mathrm{SnCl_2}\bigr) = 3 \times 0.01 = 0.03\;\text{mol}$$.

Moles and mass of Sn initially taken
Because Step 1 has a 1 : 1 stoichiometry between Sn and $$\mathrm{SnCl_2}$$,
$$n(\mathrm{Sn}) = 0.03\;\text{mol}$$.

Molar mass of Sn = 119 g mol−1, hence
$$x = n(\mathrm{Sn}) \times 119 = 0.03 \times 119 = 3.57\;\text{g}$$.

Therefore, the required mass of tin is 3.57 g.

Answer : 3.57 - 3.57