(i) Why should [Al(H2O)6] 3+ be a stronger acid than [Mg(H2O)6]2+ (ii)' Why HCl and not H2 O is liberated on heating AlCl3. 6H2O?

Explanation

(i) .[Al(H_2 O)_6]^3+. is smaller -ir size than .[Mg(H_2 O)_6]^2+. Hence .[A l(H_2 O)_6]^3+. has more
effective nuclear charge and-attracts elečtron pair from donor atoms.: Hence it is ą stronger. acid than .[Mg(H_2 O)_6]^2+.
(ii) On heating .AlCl_3^circ dot 6 H_2 O. decomposes and .A l Cl_3., undergoes hyđrolysis to from .HCl. .AlCl_3 dot 6 H_2 O rarr AlCl_3+6 H_2 O.
.AlCl_3 rarr Al(OH)_3+3 HCl.