The moles of oxygen required to react with 6.8 gram of ammonia

${\mathrm{NH}}_3+{\mathrm{O}}_2\to \mathrm{NO}+{\mathrm{H}}_2\mathrm{O}\left(\text{ unbalanced }\right)\text{ is }$____?

Balanced chemical equation:

$4{\mathrm{NH}}_3+5{\mathrm{O}}_2\to 4\mathrm{NO}+6{\mathrm{H}}_2\mathrm{O}$

Moles present in 6.8 g of ammonia:

$$\begin{gathered} \mathrm{Moles}=\frac{\mathrm{mass}}{\mathrm{molar} \mathrm{mass}} \\ =\frac{6.8 \mathrm{g}}{17 \mathrm{g}/\mathrm{mol}}=0.4 \mathrm{mol} \end{gathered}$$

4 moles of ammonia reacts with 5 moles of oxygen, the moles of oxygen required to react with 0.4 mol of ammonia:

$\mathrm{Moles} \mathrm{of} {\mathrm{O}}_2=\frac{5 \mathrm{moles} \mathrm{of} {\mathrm{O}}_2}{4 \mathrm{moles} \mathrm{of} {\mathrm{NH}}_3}\times 0.4 \mathrm{moles} \mathrm{of} {\mathrm{NH}}_3=0.5 \mathrm{moles} \mathrm{of} {\mathrm{O}}_2$