**Example 1**: A gas with 1 atmospheric pressure has 5.0 liter volume at constant temperature. If the pressure of gas is increased twice, then what will be its volume?

Given:

P_{1} = 1 atmosphere

P_{2} = twice = 2 atmosphere

V_{1} = 5.0 lit

V_{2} = ?

Solution:

P_{1}V_{1} = P_{2}V_{2}

V_{2} = P_{1}V_{1}/ P_{2}

V_{2} = 5.0 / 2 = 2.5 lit

**Example 2**: The volume of an unknown gas sample is 500ml at 25 °C temperature. If the volume of a gas is made 300 ml then what temperature will have to be kept?

V_{1} = 500 ml

T_{1} = 25 °C = 25 + 273 = 298K

V_{2} = 300 ml

T_{2} = ?

V1/V2 = T1/T2

T_{2} = T_{1}V_{2}/ V_{1}

T_{2} = 298 × 300 / 500 = 178.8 K

**Example 3**: Find out the number of moles of oxygen at 10 lit volume, 27 °C temperature and 750 mm pressure. (Atomic weight of oxygen is 16 gm/mole and constant R = 0.082 liter atm./Kelvin mole)

P = 750 mm = 750/760 atmp = 0.98 atmp

V = 10 lit

T = 27°C = 27 + 273 = 300 K

R = 0.082 lit-atmp/Kelvin mole

n = PV/RT

= 0.98 x 10 / 0.082 x 300

= 0.3983 mole of oxygen