Henry Law Formula

What is Henry’s law?

Henry’s law defines that at constant temperature, the concentration of the gas that is dissolved in a given liquid is proportional to the partial pressure of the gas above the fluid.

In chemistry, Henry’s law is a gas law stating that the amount of gas dissolved is directly proportional to its partial pressure (P) in the gas phase. This proportionality factor is termed as Henry’s law constant

The mathematical expression for Henry’s law is given by

Where,

C is the solubility of the gas at a fixed temperature in a solvent (units in M or ml gas/L).

$K_{H}$ is the Henry’s law constant (units in M/atm)

P is the partial pressure of the gas (units in Atm)

Example 1

Determine the quantity of carbon dioxide dissolved in a 1L bottle of carbonated water if the pressure of 2.4 atm is applied in the bottling process at 25 Degree Celsius? Given that $K_{H}$ of $CO_{&space;2}$ in water is 29.76 atm/(mol/L) at 25 Degree Celsius.

Solution

We know the equation

P= $K_{H}C$

Therefore,

C = P/KH

= 2.4 /29.76

= 0.08 mol/L of CO2

To convert into grams,

1 mole of CO2

= 12 + (16 x 2) = 44g

Mass of CO2 in grams  = mol of CO2 x 44 g/mol

= 8.06 x 10-2 x 44

= 3.52 g of CO2 is dissolved in 1 L of carbonated water.

Example 2

Determine the solubility of carbon dioxide in water at 0oC and pressure of 3.0 atm. Given that Carbon dioxide solubility is 0.348 g/100 mL.

Solution

We know that solubility of carbon dioxide gas is directly proportional to the pressure of the gas over the liquid.

We have the equation

P = $K_{H}C$

Therefore,

Solubility = 0.348g /100 mL x 3 atm/1 atm

= 1.044 g/100 mL of water.

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