A pressurised air tank supplies compressed air to an air engine. When the air engine is not running the absolute pressure in the tank is 300 bar and the temperature of the air is 60°C.

Typical gas molecular values:

Gas Symbol M _r (g/mol)

Hydrogen H ₂ 2

Oxygen O ₂ 32

Carbon Dioxide CO ₂ 44

Methane CH ₄ 16

Nitrogen N ₂ 28

Air (none available) 28.96

(a) The temperature of the air in the high pressure air tank when the air engine starts and the absolute pressure in the tank drops to 270 bar. Volume remains constant

(b) The mass of air in the pressurised air tank using the temperature and pressure from part 1(a).

Note: 1 m ³ = 1000 litres

1 bar = 1 x 10 ⁵ Pa

R is the universal gas constantand is always 8.314 J·K ^-1 ·mol ^-1

Tank volume = 450 litres

pV = (m/M _r )RT