Ammonia contains 82.65 % N and 17.65% H2. If the law of constant proportions is true, then the mass of nitrogen required to give 10 g Ammonia will be:

Firstly you have not written the question correctly. Ammonia has 82.35% N2. Firstly, derive the formula of Ammonia through the percentage of N2 and H2. You will get NH3.

Assuming that N2 reacts with H2 completely and no reactant is left after the reaction -

14g N2 gives 17g of NH3

#g N2 will give 10g of NH3.

So, # = 14×10/17 ≈ 8.235g.