How many grams of N2 are required to make 75 grams of NH3?

2.138 I think

Explanation:

N2 + 3H2 - > 2NH3

This means that 3 moles of H2 gives 2 moles of NH3

Lets convert 12.12 g of NH3 into moles.

The molecular weight of NH3 is 17 g/mol

So 12.12 g is 0.713 moles

If 2 NH3 comes from 3 moles of H2

1 mole comes from 1.5 moles of H2

So 0.713 moles of NH3 comes from 1.5 x 0.713 moles of H2 = 1.069 moles of H2

1 mole of H2 weights 2g

So 1.069 moles of H2 weighs 2.138 g