1. HC
CHEMISTRY HC
CHEMISTRY
CHEMISTRY IN SOCIETY
(C) CHEMICAL ENERGY

2. HC
CHEMISTRY HC
CHEMISTRY
(C) CHEMICAL ENERGY
Enthalpy of Solution

3. (B) CHEMISTRY IN SOCIETYHC
CHEMISTRY HC
CHEMISTRY
(B) CHEMISTRY IN SOCIETY
Enthalpy of solution
After completing this lesson you should be able to :
The enthalpy of solution of a substance is the enthalpy change when one mole of the substance dissolves in water.
Carry out experiments to find enthalpies of solution.

4. Enthalpy of solution COPY
The enthalpy of solution of a substance is the energy change when one
mole of a substance dissolves in water.
Higher Chemistry Eric Alan and John Harris

5. COPY
Enthalpy of solution
This is the energy change when 1 mole of solute dissolves in water
The enthalpy of solution for NaOH can be represented by the equation
NaOH(s) Na+(aq) OH-(aq)

6. Measuring enthalpy of solution
COPY
Measuring enthalpy of solution
Add 20ml water to 2 plastic beakers and take the temperature of both
Accurately record the mass of approximately 2g of the 2 solids
Add NaOH to one and record the final temperature reached
Add ammonium nitrate to the other and record the final temperature
mass (g)
start temp
( oC)
final temp
change in temp
sodium hydroxide
ammonium nitrate

7. Measuring the enthalpy of solution
COPY
Measuring the enthalpy of solution
The heat energy gained by the water (Eh) is calculated using the formula:
Eh = c m ∆T
Eh = x x
= kJ

8. Measuring the enthalpy of solution
COPY
Measuring the enthalpy of solution
The heat energy released on dissolving ……….. g of NaOH ………….. kJ
So one mole g of NaOH kJ
The enthalpy of solution of NaOH is -………….. kJ mol-1
(A negative sign is used because energy was released the temperature increased i.e. exothermic reaction)

9. Measuring the enthalpy of solution
COPY
Measuring the enthalpy of solution
The heat energy released on dissolving ……….. g of NH4NO ……….. kJ
So one mole g of NH4NO3 kJ
The enthalpy of solution of NH4NO3 is +………….. kJ mol-1
(A positive sign is used because energy was taken in the temperature decreased i.e. endothermic reaction)

10. Data book values NH4 NO3 +25.69kJ mol -1 NaOH -44.51 kJ mol -1
COPY
Data book values
NH4 NO kJ mol -1
NaOH kJ mol -1
Comment on sources of inaccuracy

11. COPY
ENTHALPIES OF SOLUTION AND HYDRATION
Salt animation solution

12. COPY
ENTHALPIES OF SOLUTION AND HYDRATION
Salt animation solution

13. COPY Enthalpy of solution 14.76 kJ mol-1
The enthalpy of solution of a substance is the energy change when one mole of a substance dissolves in water.
Worked example 1. 5g of ammonium chloride, NH4Cl, is completely dissolved in 100cm3 of water. The water temperature falls from 21oC to 17.7oC. Calculate the enthalpy of solution of ammonium chloride.
14.76 kJ mol-1 13

14. COPY Calculations for you to try.
g of ammonium nitrate, NH4NO3, is dissolved in 200cm3 of water. The temperature of the water falls from 20oC to 17.1oC. Calculate the enthalphy of solution.
COPY
When 0.1 mol of a compound dissolves in 100cm3 of water the temperature of the water rises from 19oC to 22.4oC . Calculate the enthalpy of solution of the compound.
3. The enthalpy of solution of potassium chloride, KCl, is kJ mol-1. What will be the temperature change when 14.9g of potassium chloride is dissolved in 150cm3 of water? 14

15. 1. 8g of ammonium nitrate, NH4NO3, is dissolved in 200cm3 of water
g of ammonium nitrate, NH4NO3, is dissolved in 200cm3 of water. The temperature of the water falls from 20oC to 17.1oC.
24.2 kJ mol-1

16. When 0.1 mol of a compound dissolves in 100cm3 of water the temperature of the water rises from 19oC to 22.4oC . Calculate the enthalpy of solution of the compound.
kJ mol-1

17. 3. The enthalpy of solution of potassium chloride, KCl, is + 16
3. The enthalpy of solution of potassium chloride, KCl, is kJ mol-1. What will be the temperature change when 14.9g of potassium chloride is dissolved in 150cm3 of water?
-5.34 oC 17