**Dalton’s law formula** states that the **total pressure **(P_{Total}) of the mixture of gases is equal to the sum of partial pressure of individual gases in the mixture. Here’s the formula of dalton’s law: **P**_{Total}** = P**_{1}** + P**_{2}** + P**_{3}** + …. P**_{n}

Let’s solve some problems based on this formula, so you’ll get a clear idea.

## Dalton’s Law Practice Problems

**Problem 1:** A mixture of nitrogen, oxygen and helium is filled in a cylinder. This mixture of these three gases exerts a total pressure of 12 atm on the wall of a cylinder. If the partial pressures of nitrogen and oxygen are 2 atm and 3 atm respectively, then calculate the partial pressure of helium.

Solution:

Given data:

Total pressure of the gas, P_{Total} = 12 atm

Partial pressure of the nitrogen gas, P_{1} = 2 atm

Partial pressure of the oxygen gas, P_{2} = 3 atm

Partial pressure of the helium gas, P_{3} = ?

Using the formula of dalton’s law,

P_{Total} = P_{1} + P_{2} + P_{3} + …. P_{n}

P_{Total} = P_{1} +P_{2} + P_{3} (Because, a mixture is made up of three gases)

12 = 2 + 3 + P_{3}

P_{3} = 12 – 5

P_{3} = 7 atm

Therefore, the partial pressure of the helium gas is **7 atm**.

**Problem 2:** A solid container contains a mixture of four gases whose partial pressures are 4 atm, 3 atm, 5 atm and 8 atm respectively. Calculate the total pressure of the gas.

Solution:

Given data:

Partial pressure of the gas 1, P_{1} = 4 atm

Partial pressure of the gas 2, P_{2} = 3 atm

Partial pressure of the gas 3, P_{3} = 5 atm

Partial pressure of the gas 4, P_{4} = 8 atm

Total pressure of the gas, P_{Total} = ?

Using the formula of dalton’s law,

P_{Total} = P_{1} + P_{2} + P_{3} + …. P_{n}

P_{Total} = P_{1} +P_{2} + P_{3} + P_{4} (Because, a mixture is made up of four gases)

P_{Total} = 4 + 3 + 5 + 8

P_{Total} = 20 atm

Therefore, the total pressure of the gas is **20 atm**.

**Problem 3:** A mixture of hydrogen gas and argon gas is filled in one container. Calculate the partial pressure of the argon gas, if the total pressure of the gas is 9 atm and the partial pressure of the hydrogen gas is 6 atm.

Solution:

Given data:

Partial pressure of the argon gas, P_{1} = ?

Total pressure of the gas, P_{Total} = 9 atm

Partial pressure of the hydrogen gas, P_{2} = 6 atm

Using the formula of dalton’s law,

P_{Total} = P_{1} + P_{2} + P_{3} + …. P_{n}

P_{Total} = P_{1} +P_{2} (Because, a mixture is made up of two gases)

9 = P_{1} + 6

P_{1} = 9 – 6

P_{1} = 3 atm

Therefore, the partial pressure of the argon gas is **3 atm**.

**Problem 4:** Five gases filled in the container exerts a 24 atm of total pressure on the walls of the container. The partial pressures of the four gases are 2 atm, 5 atm, 6 atm and 8 atm respectively. Calculate the partial pressure of the fifth gas.

Solution:

Given data:

Total pressure of the gas, P_{Total} = 24 atm

Partial pressure of the gas 1, P_{1} = 2 atm

Partial pressure of the gas 2, P_{2} = 5 atm

Partial pressure of the gas 3, P_{3} = 6 atm

Partial pressure of the gas 4, P_{4} = 8 atm

Partial pressure of the gas 5, P_{5} = ?

Using the formula of dalton’s law,

P_{Total} = P_{1} + P_{2} + P_{3} + …. P_{n}

24 = 2 +5 + 6 + 8 + P_{5} (Because, a mixture is made up of five gases)

24 = 21 + P_{5}

P_{5} = 24 – 21

P_{5} = 3 atm

Therefore, the partial pressure of the fifth gas is **3 atm**.

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