Identify Limiting Reactants Practice Test

Magnesium oxide forms according to $$2\text{Mg} + \text{O}_2 \rightarrow 2\text{MgO}$$. If $6.0 \text{ mol}$ of Mg and $2.0 \text{ mol}$ of $\text{O}_2$ react, which reactant is in excess (left over after the reaction stops)?

Ammonia forms according to $$\text{N}_2 + 3\text{H}_2 \rightarrow 2\text{NH}_3.$$ If $2.0\ \text{mol}$ of $\text{N}_2$ and $4.0\ \text{mol}$ of $\text{H}_2$ are available, which reactant is limiting?