The volume of an automobile air bag was 66.8 l when inflated at 25 °c with 77.8 g of nitrogen gas. what was the pressure in the bag in kpa?

We can use the ideal gas law equation assuming that nitrogen behaves as an ideal gas.
PV = nRT 
P - pressure 
V - volume - 66.8 x 10⁻³ m³
n - number of moles - 77.8 g/ 28 g/mol = 2.78 mol
R - universal gas constant - 8.314 Jmol⁻¹K⁻¹
T - temperature - 25 °C + 273 = 298 K
substituting these values into the equation 
P x 66.8 x 10⁻³ m³ = 2.78 mol x 8.314 Jmol⁻¹K⁻¹ x 298 K
P = 103.1 kPa

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