JEE Main 2013 — s Block Elements Question with Solution

Metal halide on hydrolysis with water form corresponding hydroxides. The basic strength of hydroxide increases as we move down in a group. This is because of the increase in size which results in decrease of ionization energy which weakens the strength of $\mathrm{M}-\mathrm{O}$ bonds in MOH and thus increases the basic strength. $$\begin{array}{rl}& \mathrm{Be}(\mathrm{OH}{)}_2\mathrm{Mg}(\mathrm{OH}{)}_2\\ & \text{ Amphoteric Weak base }\\ & \mathrm{Ca}(\mathrm{OH}{)}_2\mathrm{Sr}(\mathrm{OH}{)}_2\mathrm{Ba}(\mathrm{OH}{)}_2\\ & \end{array}$$ Hence, $\mathrm{Be}(\mathrm{OH}{)}_2$ will have lowest $\mathrm{pH}$.