Effect of Temperature on Solubility
This is part of the HSC Chemistry course under the topic Solution Equilibria
HSC Chemistry Syllabus
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Derive equilibrium expressions for saturated solutions in terms of Ksp and calculate the solubility of an ionic substance from its Ksp value
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Predict the formation of a precipitate given the standard reference values for Ksp
Effect of Temperature on Solubility
- Since the equilibrium constant changes with constant, the value of solubility product Ksp also changes with temperature.
- If dissolution of an ionic compound is endothermic, an increase in temperature will increase Ksp which in turn increases the solubility of the solution. The effect is opposite if temperature is reduced.
- If dissolution of an ionic compound is exothermic, a decrease in temperature will increase Ksp which in turn increases the solubility of the solution. The effect is opposite if temperature is increased.
Table: Effect of changing temperature on the solubility of ionic compounds.
|
|
Endothermic dissolution |
Exothermic dissolution |
|
Increase in temperature |
Ksp increases, solubility increases |
Ksp decreases, solubility decreases |
|
Decrease in temperature |
Ksp decreases, solubility decreases |
Ksp increases, solubility increases |
Practice Questions
1. Consider the Ksp values of AgCl and BaSO4 at 25 ºC.
The Ksp of AgCl at 100ºC is 2.15 ´ 10–8.
The Ksp of BaSO4 at 18ºC is 1 ´ 10–10.
Explain whether the dissolution of AgCl and BaSO4 is endothermic or exothermic.
2. When a particular ionic compound is added to a beaker of water, the temperature of the water increases. After a while, some amount of precipitate is observed at the bottom of the beaker.
Explain what will happen to the precipitate if the solution is heated.
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