# Henry’s law equation

Henry’s law equation, represented by C = k P, describes the relationship between the concentration of a dissolved gas (C) in a given quantity of liquid and the partial pressure (P) of that gas. In this equation, k is a constant known as Henry’s law constant, which is specific to each gas-liquid system.

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## Practice problems

### Problem #1

Calculate the concentration of oxygen gas dissolved in water, given that the partial pressure of the gas is 4 atm and the Henry’s law constant, k = 15 L atm/mol.

Solution

Given data:

• Concentration of a dissolved gas, C = ?
• Partial pressure of the gas, P = 4 atm
• Henry’s law constant, k = 15 L atm/mol

Applying the formula:

• C = k P
• C = 15 × 4
• C = 60 mol/L

Therefore, the concentration of a helium gas dissolved in water is 60 mol/L.

### Problem #2

A liquid bottle contains a hydrogen gas concentration of 14 mol/L. Calculate the partial pressure of the gas, if the Henry’s law constant, k = 7 L atm/mol.

Solution

Given data:

• Concentration of a dissolved gas, C = 14 mol/L
• Partial pressure of the gas, P = ?
• Henry’s law constant, k = 7 L atm/mol

Applying the formula:

• C = k P
• 14 = 7 × P
• P = 2 atm

Therefore, the partial pressure of the gas is 2 atm.

### Problem #3

If the partial pressure of argon gas in water is 6 atm and the Henry’s law constant is 25 L atm/mol, what is the concentration of argon gas dissolved in water?

Solution

Given data:

• Partial pressure of the gas, P = 6 atm
• Henry’s law constant, k = 25 L atm/mol
• Concentration of a dissolved gas, C = ?

Applying the formula:

• C = k P
• C = 25 × 6
• C = 150 mol/L

Therefore, the concentration of an argon gas dissolved in water is 150 mol/L.

### Problem #4

Calculate the partial pressure of a hydrogen gas dissolved in water, given a concentration of 20 mol/L and the Henry’s law constant, k = 5 L atm/mol.

Solution

Given data:

• Partial pressure of the gas, P = ?
• Concentration of a dissolved gas, C = 20 mol/L
• Henry’s law constant, k = 5 L atm/mol

Applying the formula:

• C = k P
• 20 = 5 × P
• P = 4 atm

Therefore, the partial pressure of the gas is 4 atm.