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Enthalpy of Solution (  H SOLN ). When substances dissolve in water, an energy change usually occurs. Enthalpy of solution is defined as the enthalpy.

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Presentation on theme: "Enthalpy of Solution (  H SOLN ). When substances dissolve in water, an energy change usually occurs. Enthalpy of solution is defined as the enthalpy."— Presentation transcript:

1 Enthalpy of Solution (  H SOLN )

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 50cm 3 of H 2 O Thermometer Balance 2g NaOH or 4g NH 4 NO 3

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 5 o C. 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 moles: 1.045kJ 1 mole : 40.2kJ

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


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