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JAMB Chemistry 2007 Question 22

Question 22

Energy Changes

Dissolving some pellets of NaOH in water would result in

  1. A.a decrease in the free energy of the solution
  2. B.a decrease in the entropy of the solution
  3. C.a lowering of the temperature of the solution
  4. D.an increase in the entropy of the solution.
Show the answer and explanation

Answer: D (an increase in the entropy of the solution.)

Explanation

When solid NaOH dissolves, its ordered lattice breaks up into ions spread through the water, so the disorder (entropy) increases. The process gives out heat, so the temperature rises.