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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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Answer Text:
Experiment: To measure the molar enthalpy change for the dissolution (enthalpy of solution) for various compounds:
(i) Procedure;
- A clean 250#cm^3# glass or plastic beaker is wrapped with a newspaper leaf.
- About 50#cm^3# of tap water is measured into the beaker and the steady temperature noted.
- The beaker is held in a tilted position and 2#cm^3# of and sulphuric acid added into the water.
(ii) Apparatus:
figreactionrates23720201535.JPG
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.
figreactionrates23720201536.JPG
Calculate the enthalpy change (ΔHsoln) in each experiment done. Additional information;
- Density of concentrated Sulphuric acid =1.84g#cm^-3#
- Density of water =1g#cm^-3#
- No change in volume when any of the solids dissolved in water
- The specific heat capacities of the solutions=#4.2kjkg^-1k^-1#
figreactionrates2372020537.JPG
figreactionrates23720201538.JPG