# Behaviour of Gas

## 1. Boyle's law

At constant temperature, the volume of a definite mass of a gas is inversely proportional to pressure.

V α 1/p (at constant T) or, V = K.1/p
pV= K (where K is a constant)
p1V1 = p2V2

## 2. Charle's law

At constant pressure, the volume of a definite mass of a gas is directly proportional to absolute temperature.

V α T (at constant p) or, V = K.T
V/T = k
V1 /T1 = V2 / T2

## 3. Gay-Lussac's law

At constant volume, the pressure of given mass of a gas is directly proportional to the temp in Kelvin.

p α T (at constant V) or, p= K . T
or, p/T = K
p1 / T1 = p2 / T2

## 4. Avogardo's gas law

At constant temperature and pressure the volume of a gas is directly proportional to the number of molecules.
V α n (at constant T & p)

## 5. Ideal gas equation

pV = nRT is called ideal gas equation.
Where,
p = Pressure,
V = volume
n = number of mole
T = temperature in Kelvin.
R = gas constant
= 0.0821 lit atm K-1 mol-1
= 8.314 JK-1 mol-1
= 1.987 cal K-1 mol-1

## 6. S.T.P. & N.T.P.

S.T.P. — Standard temperature and pressure
N.T.P. — Normal temperature and pressure

At S.T.P., for 1 mole gas
V= 22.4 litre = 22400 ml
p = 1 atm = 76 cm of Hg = 760 mm of Hg T= 273 K