The monomer (X) involved in the synthesis of Nylon 6,6 gives positive carbylamine test. If 10 moles of X are analyzed using Dumas method, the amount (in grams) of nitrogen gas evolved is ________.

Use: Atomic mass of N (in amu) = 14

Nylon 6,6 is prepared by condensation of hexamethylenediamine and adipic acid.
Only primary amines give the carbylamine test, therefore the monomer $$X$$ must be the diamine:

$$X \;=\; NH_2\!-\!(CH_2)_6\!-\!NH_2 \;$$ (hexamethylenediamine)

Each molecule of $$X$$ contains two nitrogen atoms.

Number of moles of $$X$$ taken  =  10

Moles of nitrogen atoms present
$$= 10 \times 2 = 20 \text{ mol of N-atoms}$$

In the Dumas method all the nitrogen is converted to molecular nitrogen: $$2\,\text{N-atoms} \rightarrow N_2$$.
Hence, moles of $$N_2$$ formed
$$= \frac{20}{2} = 10 \text{ mol}$$

Mass of $$N_2$$ evolved
$$= 10 \text{ mol} \times 28 \text{ g mol}^{-1} = 280 \text{ g}$$

Therefore, the amount of nitrogen gas obtained is 280 g.