Equilibrium Question 821
Question: Equimolar solutions of the following compounds are prepared separately in water. Which will have the lowest pH value-
Options:
A) $ BeCl_2 $
B) $ SrCl_2 $
C) $ CaCl_2 $
D) $ MgCl_2 $
Show Answer
Answer:
Correct Answer: A
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 $ M-O $ bonds in MOH and thus increases, the basic strength. $ \underset{Amphoteric}{\mathop{Be{{( OH )}_2}}},~~\underset{Weakbase}{\mathop{Mg{{( OH )}_2}}}, $
$ Ca{{( OH )}_2}\underset{Strongbase}{\mathop{Sr{{(OH)}_2}}},Ba{{( OH )}_2} $ Hence, $ Be{{(OH)}_2} $ will have lowest pH.
