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Metals form basic hydroxides. Which of the following metal hydroxide is the least basic?
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Verified Answer
The correct answer is:
$\mathrm{Mg}(\mathrm{OH})_2$
$\mathrm{Mg}(\mathrm{OH})_2$
The basic character of the given hydroxides increases down the group due to decrease in ionization enthalpies. On moving down the group, the ionic size increases, so $\mathrm{M}-\mathrm{O}$ bond in metal hydroxides gets weaker and easily gives $\mathrm{OH}^{-}$in the solution and I.E. further decreases. Hence, $\mathrm{Mg}(\mathrm{OH})_2$ will be least basic. The order of basicity will be:
$$
\mathrm{Mg}(\mathrm{OH})_2 < \mathrm{Ca}(\mathrm{OH})_2 < \mathrm{Sr}(\mathrm{OH})_2 < \mathrm{Ba}(\mathrm{OH})_2
$$
$$
\mathrm{Mg}(\mathrm{OH})_2 < \mathrm{Ca}(\mathrm{OH})_2 < \mathrm{Sr}(\mathrm{OH})_2 < \mathrm{Ba}(\mathrm{OH})_2
$$
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