Enter the mass of the solution (often approximated as the solvent mass), the specific heat capacity (often approximated as the solvent’s), the measured temperature change (ΔT = Tfinal − Tinitial), and the moles of solute into the calculator to determine the molar heat (enthalpy) of dissolution.

Heat Of Dissolution Calculator

Enter any 4 values to calculate the missing variable

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Heat of Dissolution Formula

The following formula is used to calculate the molar enthalpy (heat) of dissolution from a simple calorimetry measurement, assuming heat losses and the calorimeter heat capacity are negligible.

\Delta H_{\text{diss}} = -\frac{m \cdot c \cdot \Delta T}{n}

Variables:

  • ΔHdiss is the molar enthalpy (heat) of dissolution (J/mol)
  • m is the mass of the solution (g) (often approximated as the solvent mass for dilute solutions)
  • c is the specific heat capacity of the solution (J/g°C) (often approximated as the solvent’s)
  • ΔT is the measured temperature change of the solution, ΔT = Tfinal − Tinitial (°C or K)
  • n is the moles of solute dissolved (mol)

First compute the heat gained by the solution: qsln = m·c·ΔT (in joules). Then the molar enthalpy of dissolution is ΔHdiss = −qsln/n. With this sign convention, a positive ΔT (solution warms) gives a negative ΔHdiss (exothermic), and a negative ΔT gives a positive ΔHdiss (endothermic).

What is Heat of Dissolution?

The heat of dissolution (enthalpy of dissolution) is the enthalpy change when a solute dissolves in a solvent at (approximately) constant pressure, commonly reported per mole of solute. This process can either be endothermic (absorbing heat from the surroundings) or exothermic (releasing heat to the surroundings), depending on the solute and solvent involved. It is an important parameter in thermodynamics and chemistry because it describes the energy change associated with forming a solution.

How to Calculate Heat of Dissolution?

The following steps outline how to calculate the Heat of Dissolution.

  1. First, determine the mass of the solution (m) (often approximated as the solvent mass).
  2. Next, determine the specific heat capacity (c) (often approximated as the solvent’s).
  3. Next, measure the temperature change of the solution: ΔT = Tfinal − Tinitial.
  4. Next, determine the moles of solute dissolved (n).
  5. Finally, calculate the molar enthalpy of dissolution using ΔHdiss = −(m · c · ΔT) / n.
  6. After inserting the values and calculating the result, check your answer with the calculator above.

Example Problem : 

Use the following variables as an example problem to test your knowledge.

Mass of Solvent (m) = 100 g

Specific Heat of Solvent (c) = 4.18 J/g°C

Change in Temperature (ΔT) = 10 °C

Moles of Solute (n) = 0.5 mol

qsln = m·c·ΔT = (100 g)(4.18 J/g°C)(10 °C) = 4180 J, so ΔHdiss = −qsln/n = −4180/0.5 = −8360 J/mol (−8.36 kJ/mol).