1.0 g of magnesium is burnt with 0.56 g O₂ in a closed vessel. Which reactant is left in excess and how much (At. wt. Mg = 24; O = 16)

The balanced chemical reaction is shown below:
              $\mathrm{Mg} + \frac{1}{2} {\mathrm{O}}_2 \to \mathrm{MgO}$
Moles:   $\frac{1.0}{24};\frac{0.56}{32}$​

              $\frac{0.5}{12};\frac{0.07}{4}$​

               $\frac{0.5}{12}- \mathrm{x};\frac{0.07}{4}-\frac{\mathrm{x}}{2}$​
Oxygen is limiting reagent so, $\frac{0.07}{4}-\frac{\mathrm{x}}{2}=0$
$\mathrm{x}=\frac{0.07}{2}$
Excess Mg = $\frac{0.5}{12}-\frac{0.07}{2} \mathrm{mol}$
Mass of Mg is = 1 − 0.07 × 12 = 0.16 g
Thus, when 1.0 g of magnesium is burnt with 0.56 g O_2​ in a closed vessel, 0.16 g of magnesium is left in excess.