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# Form 4 Chemistry: Energy changes in chemical and physical processes lessons

Experiment: To measure the molar enthalpy change for the dissolution (enthalpy of solution) for various compounds.

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Experiment: To measure the molar enthalpy change for the dissolution (enthalpy of solution) for various compounds:
(i) Procedure;
- A clean 250cm^3 glass or plastic beaker is wrapped with a newspaper leaf.
- About 50cm^3 of tap water is measured into the beaker and the steady temperature noted.
- The beaker is held in a tilted position and 2cm^3 of and sulphuric acid added into the water.
(ii) Apparatus:

Caution:
- Concentrated sulphuric acid should always be added to water and never vise versa.
Reason:
- The mixture is then carefully but vigorously stirred using a thermometer and the highest temperature of the solution recorded.
The experiment is repeated with other compounds:
-Ammonium nitrate solid
-Potassium nitrate solid
-Sodium hydroxide pellets.
-Sodium nitrate solid Results and observations.

Calculate the enthalpy change (ΔHsoln) in each experiment done. Additional information;
- Density of concentrated Sulphuric acid =1.84gcm^-3
- Density of water =1gcm^-3
- No change in volume when any of the solids dissolved in water
- The specific heat capacities of the solutions=4.2kjkg^-1k^-1