Q25Short answer
Ionisation constant of a weak base MOH, is given by the expression + – [M ][OH ] Kb = [MOH] Values of ionisation constant of some weak bases at a particular temperature are given below: Base Dimethylamine Urea Pyridine Ammonia –4 –14 –9 –5 Kb 5.4 × 10 1.3 × 10 1.77 × 10 1.77 × 10 Arrange the bases in decreasing order of the extent of their ionisation at equilibrium. Which of the above base is the strongest?
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• Order of extent of ionisation at equilibrium is as follows : Dimethylamine > Ammonia > Pyridine > Urea • Since dimethylamine will ionise to the maximum extent it is the strongest base out of the four given bases. – – – –