Partial Pressure Calculator

An online partial pressure calculator is properly designed to calculate partial pressure, volume, temperature, and amount of moles of each individual gas enclosed in a container. Before you move further, you need to understand important gas laws which are explained below.

Keep reading!

What Is A Partial Pressure?

In the context of chemistry:

“In a mixture of gases, the pressure exerted by each individual gas separately is known as the partial pressure.”

For example:

Partial pressures of some important gases are as follows:

Partial Pressure Formula:

Uptill now many theories have been published for calculating partial pressure in a gas mixture. Some of the important gas laws that are widely used to calculate the partial pressure are as follows:

Dalton’s Law Of Partial Pressure:

This law states that:

“In a mixture of gases that is enclosed in a container, the total pressure exerted on the walls of the container is actually equal to the sum of the individual partial pressures exerted by each gas separately”

Dalton’s Law Of Partial Pressure Formula:

Total Pressure = P₁ + P₂ + ... + Pₙ

The equation for partial pressure is as follows:

Partial Pressure = Total Pressure × Mole Fraction

Mole Fraction: "It is defined as the ratio of the number of moles of selected gas to the number of moles of the entire gas". Mathematically:

Mole Fraction = (No. of Moles of Selected Gas) / (No. of Moles of Entire Gas Mixture)

Also, you can use a free online mole fraction calculator to find the exact results for this quantity.

Ideal Gas Law:

This gas law is a generic law which supports the relationship among different properties of an ideal gas. The relationship equation is given below:

P × V = n × R × T

Where:

P = Pressure of the gas

V = Volume of the gas

n = No.of moles of the gas

T = Temperature of gas

R = Universal gas constant

R = 8.3145 J/(mol·K)

R = 0.08206 atm·L·mol⁻¹·K⁻¹

8.3145ol∗K​

0.08206t..o−1.−1

Now if we divide the product of number of moles of a specific gas, temperature, and gas constant by volume of the entire mixture, we can get the partial pressure formula to determine this specific term accurately:

Pᵢ = (nᵢ × R × T) / V

Where:

P_i = Partial pressure of the individual gas

n_i = No. of moles of the individual gas

T = Temperature of the whole gas mixture

V = Volume of the whole gas mixture

Henry’s Law:

This is indeed the most important partial pressure gas law considered so far. This law states that:

“ The amount of the gas dissolved in a certain liquid and the partial pressure of the gas accumulated above the surface of that liquid are proportional to each other”

Partial Pressure Equation:

Here we have two different methods to find the partial pressures of individual gases:

Method #1:

When you are given the concentration of the solution:

\( P = K_{H1} \cdot \text{Concentration} \)

Where \( K_{H1} \) = Henry’s law constant in units of [L·atm/mol].

Method #2:

When the solute’s mole fraction is given:

\( P = K_{H2} \cdot \chi \)

Where \( K_{H2} \) = Henry’s law constant in atm.

Examples:

Example 1:

The total pressure of a mixture of hydrogen and oxygen is 2.3 atm. If the partial pressure of hydrogen is 2 atm, find the mole fraction of oxygen.

Solution:

Total Pressure: \( P_\text{total} = P_{H_2} + P_{O_2} \)

\( 2.3 = 2 + P_{O_2} \implies P_{O_2} = 0.3 \, \text{atm} \)

Mole fraction of oxygen: \( \chi_{O_2} = \frac{P_{O_2}}{P_\text{total}} = \frac{0.3}{2.3} \approx 0.13 \)

Example 2:

Gas A: 20 L at 1 atm, Gas B: 10 L at 3 atm, both in a 10 L container at 200 K. Find total pressure.

Solution:

Using ideal gas law: \( PV = nRT \)

Number of moles Gas A: \( n_A = \frac{P V}{R T} = \frac{1 \cdot 20}{0.08206 \cdot 200} \approx 1.21 \, \text{mol} \)

Number of moles Gas B: \( n_B = \frac{3 \cdot 10}{0.08206 \cdot 200} \approx 1.82 \, \text{mol} \)

Total moles: \( n_\text{total} = n_A + n_B \approx 3.03 \, \text{mol} \)

Total pressure in 10 L container: \( P_\text{total} = \frac{n_\text{total} R T}{V} \)

Example 3:

Four gases A, B, C, D exert pressures 3 atm, 2 atm, 5 atm, and 4 atm. Find total pressure:

Solution:

\( P_\text{total} = P_A + P_B + P_C + P_D = 3 + 2 + 5 + 4 = 14 \, \text{atm} \)

Example 4:

Given Henry’s constant \( K_H = 2.313 \, \text{L·atm/mol} \) at 198 K, solubility \( C = 2.41 \times 10^{-4} \, \text{M} \). Find partial pressure:

Solution:

\( P = K_H \cdot C = 2.313 \cdot 2.41 \times 10^{-4} \approx 0.00056 \, \text{atm} \)

How Partial Pressure Calculator Works?

Well, our free calculator finds the accurate outputs regarding various important terms for gases. But it does not mean that you can not use it. We have designed it in such a way that you will never feel difficulty in using it. For instance, let us guide you how to use it?

Input:

First, you need to select one of the following methods:

• Dalton’s law of partial pressure
• Ideal gas law
• Henry’s law (Method 1)
• Henry’s method (Method 2)

If you select Dalton’s law method, further select either of the given options in “To Calculate” drop down menu:

• Partial pressure
• Mole fraction
• Enter Required parameter values
• Hit the calculate button

If you select Ideal Gas Law, further make a choice about what you need to determine from the following in “To Calculate” drop down list:

• Partial pressure
• Volume
• Temperature
• Amount of moles
• Click on calculate

If you choose Henry’s method 1, make a further selection about what you wish to find from the following:

• Partial pressure
• Concentration
• Tap the calculate button

In case you do choose Henry’s method 2, choose what next you wish to work for which can be either of the following:

• Partial pressure
• Mole fraction
• Hit the calculate button

Output:

The free henry’s law calculator determines:

• Partial pressure
• Mole fraction
• Volume
• Concentration
• Temperature
• Amount of moles

FAQ’s:

What do you mean by an ideal gas?

A hypothetical gas that consists of many point particles having no forces among them is called an ideal gas.

What does Boyle's law demonstrate?

Boyle’s law determines the relationship between a gas volume and pressure. It states that: “The pressure that is exerted by a gas is always inversely proportional to the volume of the gas, keeping the temperature constant”.

Why ice occupies more space than water?

Yes, it is true that ice always occupies more space than water. This is because when water molecules freezes, they occupy 9% more space than before.

Conclusion:

Without partial pressure, we are actually unable to make an estimation about gases. Chemists widely use free online partial pressure calculator while performing various chemical reactions. This is because this calculator gives most accurate results that are very crucial to avoid any disturbance in the reaction.

References:

From the source of Wikipedia: Kinetic theory of gases, Equilibrium properties, Transport properties.

From the source of Khan Academy: real gases, Deviations from ideal behavior, The van der Waals equation, Non-ideal behavior of gases.

From the source of Lumen Learning: Charles’ and Gay-Lussac’s Law, Extrapolation to Zero Volume.