The following is a Limiting Reactant problem:
Magnesium nitride is formed in the reaction of magnesium metal with nitrogen gas in this reaction: 3 Mg(s) + N2(g) Mg3N2(s)
How many grams of product are formed from 2.0 mol of N2 (g) and 8.0 mol of Mg(s)?

Question

The following is a Limiting Reactant problem:
Magnesium nitride is formed in the reaction of magnesium metal with nitrogen gas in this reaction:  3 Mg(s) + N2(g)  Mg3N2(s)
	How many grams of product are formed from 2.0 mol of N2 (g) and 8.0 mol of Mg(s)?

jfraser · Answer

since you know both the amounts of $N_2$ and $Mg$ you start with, compare the mole ratio that the balanced reaction says you $need$ with the molar amounts the problem says you $have$

jfraser · Answer

the balanced reaction tells you that for every 1 mole of $N_2$, you $need$ three times that much $Mg$ in order to use everything up

You $have$ two moles of $N_2$, so how many moles of $Mg$ should be used?