Partial pressure in terms of mole fraction

• Let three gases be enclosed at

T = temperature three gases,
V = volume,
p1, p2 and p3 = partial pressure exerted on three gases respectively.

• P_{A =} x_A p_Total

Similarly, p_{B =} x_B p_Total

P_{C =} x_C p_Total

Problem:

A mixture of dihydrogen and dioxygen at one bar pressure contains 20% by weight of dihydrogen. Calculate the partial pressure of dihydrogen.

Solution:

Pressure of the gas mixture = 1 bar

Let the amount of mixture = 100g

Mass of hydrogen in mixture = 20 g

Mass of oxygen in mixture = 80 g

n_H = 20/ 2  = 10 mol

n_O = 80 / 32 = 2.5 mol

Using the formula,

p_H = X_H x P_total = (n_H / n_{H +} n_O) x P _total   = (10 / 10 + 2.5 ) x  1 

= 0.8 bar

Kinetic molecular theory of gases

• Molecules are point masses having no volume.
• Gas atoms apply no constrain on different atoms unless they suffer collision.
• Collisions of particles with each other or with the boundaries of container do not result in decreased energy system.
• The atoms of a gas are in consistent and irregular movement.
• The temperature of a gas relies upon its average kinetic energy 1/2 mv² = 3/2 KT
• Ideal gas possesses kinetic energy.

Behaviour of real gases: deviation from ideal gas behaviour

• The isotherm obtained in the graph by plotting the pressure (P) vs Volume (V) for real gas does not coincide with the slope of ideal gas.