Henry Law Formula

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.

Henry Law Formula

The Henry’s law constant is the expression for equilibrium distribution of a compound between water and gaseous phase denoted by KH. It indicates the volatility of the compound.

The mathematical expression for Henry’s law is given by

$K_{H}=\frac{P_{1}}{C_{w}}$

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)

$P_{gas}$ 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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