# What is gas stoichiometry?

Aug 29, 2014

Gas stoichiometry is the study of the relative amounts of reactants and products in reactions that involve gases.

EXAMPLE
Calculate the volume of gaseous NO₂ produced by the combustion of 100 g of NH₃ at 0°C and 100 kPa.

Solution

Step 1. Write the balanced chemical equation.

4NH₃(g) + 7O₂(g) → 4NO₂(g) + 6H₂O(l)

Step 2. Convert mass of NH₃ → moles of NH₃ → moles of NO₂.

100 g NH₃ × $\left(1 {\text{mol NH"_3)/(17.03"g NH"_3) × (4"mol NO"_2)/(4"mol NH}}_{3}\right)$ = 5.872 mol NH₃ (3 significant figures +
1 guard digit)

Step 3. Use the Ideal Gas Law to calculate the volume of NO₂.

$P V = n R T$

$V = \frac{n R T}{P} = \left(5.872 \text{mol" × 8.314"kPa·L·K"^-1"mol"^-1 × 273"K")/(100 "kPa}\right)$ = 133 L