The Volume, V
The volume of the container is the volume of the gas sample. It is usually given in litre (l or L) or
millilitres (ml or mL).1 1itre(l) = 1000 ml and 1 ml = 10–3 l One millilitre is practically equal to one cubic centimetre (cc). Actually1 litre(l) = 1000.028 cc The SI unit for volume is cubic metre (m3 and the smaller unit is decimeter3
(dm).
The pressure of a gas is defined as the force exerted by the impacts of its molecules per unit surface area in contact. The pressure of a gas sample can be measured with the help of a mercury manometer Similarly, the atmospheric pressure can be determined with a mercury barometer
The pressure of air that can support 760 mm Hg column at sea level, is called one atmosphere
(1 atm). The unit of pressure, millimetre of mercury, is also called torr.
Thus,
1 atm = 760 mm Hg = 760 torr
The SI unit of pressure is the Pascal (Pa). The relation between atmosphere, torr and pascal is :
1 atm = 760 torr = 1.013 × 105Pa
The unit of pressure ‘Pascal” is not in common use.