How many moles of ammonia (nh3) would be produced if 2.5 moles of nitrogen (n2) reacted with excess hydrogen (h2)?

Firstly, a balanced equation has to be written for the production of ammonia (NH₃) from hydrogen gas (H₂) and nitrogen gas (N₂):
                    N₂   +   3H₂   →   2NH₃

Now, the mole ratio of N₂ : NH₃ is 1 : 2 based on the coefficients of the balanced equation.

If the moles of N₂ = 2.5 moles

   then the moles of NH₃ produced = 2.5 mol × 2 
                                                          =  5 mol

Thus, the moles of ammonia produced when 2.5 mol of nitrogen gas is combined with excess hydrogen gas is 5 mol.

The answer is a) carbon-12

Nonmetals usually react by gaining electrons