1. Enthalpy of Solution (HSOLN)

2. When substances dissolve in water, an energy change usually occurs.
Enthalpy of solution is defined as the enthalpy change when 1 mole of a substance completely dissolves (kJ mol-1)

3. Experiment
50cm3 of H2O
Thermometer
Balance
2g NaOH or 4g NH4NO3

4. Measurements Taken Volume (mass) of water Mass of substance dissolves
Temperature of water at start
Temperature of water at end

5. Specimen Results
1.03g of NaOH was dissolved in 50g (0.05kg) of water. The temperature of water rose by 5oC.
Calculate the enthalpy of solution of NaOH.

6. 1. Calculate energy change
EH = c x m x ΔT
= 4.18x0.05x5
= kJ
2. Calculate the number of moles of NaOH
1 mole NaOH=40g
so 1.03g=1.03/40= mol
3. Calculate enthalpy of solution
0.026 moles: 1.045kJ
1 mole : 40.2kJ

7. Therefore the Enthalpy of solution= -40.2kJ
Note that HSOLN can be a +ve or –ve value.
You can work out which it is from the question.