A balanced equation tells you the mole ratio of all reactants and products. Using the chemical reaction below how many moles of NH3 are made when 3 moles of hydrogen gas are used?

2N2 + 3H2 - - - > 2NH3

From the reaction above 2 moles of N2 reacted with 3 moles of H2 to give 2 moles of ammonia

THese implies that the mole ratio of hydrogen to ammonia is 3:2

Therefore if 3 moles of hydrogen were used the moles of ammonia is therefore

(3 x2) / 3 = 2moles

By using the mole ratio, we can determine that 2 moles of NH3 are made when 3 moles of hydrogen gas are present. The numbers in front of the chemicals tell us the relative amounts consumed and produced. Since there is a 3 in front of H2 and a 2 in front of NH3, this tells us that for every 3 moles of H2 gas used, 2 moles of NH3 are made.