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Equimolar solutions of the following were prepared in water separately. Which one of the solutions will record the highest pH ?
A
$MgCl_2$
B
$CaCl_2$
C
$SrCl_2$
D
$BaCl_2$
Detailed Solution
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.
$Be(OH)_2$ 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.