How to Find Partial Pressure

How to Find Partial Pressure of Gases in a Mixture using Ideal Gas Law?

Partial Pressure of Gases Calculation

The pressure that is exerted by a gas in a mixture of gases is termed as the partial pressure. The partial pressure of each gas can be calculated using various methods, where as this tutorial is based on the ideal gas law PV = nRT. Use this simple step by step tutorial to learn how to find partial pressure of gases in a mixture.

Formula :
Based on Ideal Gas Law,
P = nRT / V
Where,
P = Partial Pressure
n = Number of Moles
R = Molar Gas Constant
T = Temperature
V = Volume

Step 1 : Consider a a mixture of 2.00 g of H₂ and and 4g of CO₂ is added in a 2.0 L of container at a temperature of 298 Kelvin. Find the partial pressure of H₂.
Given,
Combustion Amount / Volume, V = 2 L.
Temperature, T = 298 K
Molar Gas Constant, R = 8.314 K-1mol-1

Step 2: We have to know the number of moles of H₂ to find the partial pressure,
To find number of moles(n),
n = Combustion Amount / Molar Mass

We know, Molar Mass of H₂ =2.01588 g/mol
Hence,
n = 2 / 2.01588
= 0.992

Step 3 :Apply the values in the formula,
P = (0.992 x 8.314 x 298) / 2
= (8.247 x 298) / 2
= 2457.75 / 2
= 1228.87 kPa

Hence, based on the Ideal Gas Law, calculated partial pressure of H₂ is 1228.87 kPa