Temperature effects on solubility products are readily assessed as most solubility reactions are clearly
seen as endothermic and disorder increasing. Raising the temperature will thus increase Ksp together
with the solubility of the solid.
Problems
(1) Calculate the concentration of sodium acetate needed to produce a pH of 5.0 in a solution of acetic
acid (0.1 M) at 25°C. pKa for acetic acid is 4.756 at 25°C.
(2) What is the pH at 25°C of a solution which is 1.5 M with respect to formic acid and 1 M with
respect to sodium formate? pKa for formic acid is 3.751 at 25°C.
(3) Ca lculate the pH of a 2 M solution of sodium benzoate. pKa for benzoic acid is 4.01 at 25°C. pKw =
(4) What is the pH of a 0.025 M solution of ammonium acetate at 25°C? pKa of acetic acid at 25°C is
4.76, pKa of the ammonium ion at 25°C is 9.25, pKw = 14.
Further Reading
Betteridge, J. & Hallam, H. E., Modern Analytical Methods, RSC Monograph. London, 1973.
Blackburn, T. R., Equilibrium, Holt, Rinehart & Winston, New York, 1969.
Hartley, F. R., Burgess, C. & Alcock, R., Solution Equilibrium, Ellis Horwood Chichester, 1980.
Jefferey, G. H., Bassett, J., Mendham, J & Denney, R. C., Vogel's Textbook of Quantitiative Chemical
Analysis (5th edn), Longman, 1989.
Perrin, D. D., Masking and Demasking of Chemical Reactions, Wiley, New York, 1970.
Perrin, D. D., Organic Complexing Reagents: Structural Behaviour and Application to Inorganic
Analysis, Knieger, 1979.