Question

Automatic air bags are inflated with nitrogen gas, which is formed by the decomposition of solid sodium azide (NaN3). The other product is sodium metal. Calculate the volume of nitrogen gas at 27 °C and 756 torr formed by the decomposition of 125 g of sodium azide.

Answer 1

2 NaN3 -------------------- 3 N2 + 2 Na

mass of NaN3= 125 grams

Molar mass of NaN3= 65 gram/mole

number of moles of NaN3= 125/65= 1.923 mole

according to equation

2 mole of NaN3= 3 mole of N2

1.923 mole of NaN3= ?

                      = 3 x 1.923/2= 2.8845 moles of N2

number of moles of N2= 2.8845 moles

T= 27C = 27+273= 300K

Pressure = P= 756 torr= 0.994737 atm                   [1 torr= 0.00131579 atm]

R= 0.0821 L-atm/mole-k

PV= nRT

V= nRT/P= 2.8845 x 0.0821 x 300/0.994737 = 71.42L

Volume of N2= 71.42 L