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Alkaline Earth Metals: Basic Character of Hydroxides
Concepts tested here
- Basic strength of group 2 hydroxides
All Questions
2008 AIPMT 1 question
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Equimolar solutions of the following were prepared in water separately. Which one of the solutions will record the highest pH ?Equimolar solutions of the given chlorides, when prepared in water, form their respective hydroxides to a small extent by hydrolysis of the cation.
$Be(OH)_2$ is amphoteric, but the hydroxides of the other alkaline earth metals are basic.
The basic strength of the hydroxides increases down the group: $Mg(OH)_2 \lt Ca(OH)_2 \lt Sr(OH)_2 \lt Ba(OH)_2$
A small, highly charged cation like $Mg^{2+}$ hydrolyses the most and makes its solution slightly acidic; the large $Ba^{2+}$ ion hydrolyses the least.
Higher the basic character of the hydroxide, higher will be the pH of the solution.
So the $BaCl_2$ solution will record the highest pH.