Heat Of Solution Formula

The heat solution is defined as the difference in the enthalpy related to the dissolving substance in a solvent at constant pressure which is leading in infinite dilution. The unit of solution enthalpy is KJ/mol.

The enthalpy change is observed when the solute is dissolved in the solvent. When solid or gas is dissolved in the solvent the heat is absorbed. This process is known as heat dissolution or heat solution. The heat solution is measured in terms of a calorimeter.

Formula of Heat of Solution

The formula of the heat of solution is expressed as,

ΔHwater = mass water × ΔTwater × specific heat water


ΔH = heat change

mass water = sample mass

ΔT = temperature difference

Specific heat = 0.004184 kJ/gC.

Solved Examples

Example 1

The heat absorbed when hydrated salt (Na2CO3.10H2O) is dissolved at 291K isothermally in a large quantity of water is 65 KJ per mole solute. Determine the heat of crystallization of 1 kg Na2CO3.10H2O.


Given data:

m = 65 kJ per mol

ΔT = 291K

Specific heat = 0.004184 KJ/gC

Substitute in the given formula, we get

ΔHwater= masswater  × ΔTwater × specific heatwater

         = 65 × 291 × 0.004184

Therefore, ΔHwater = 79.140 kJ/Kg solute

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