(Solved): H+,Mg2+,NH3,AlCl3 (iii) Which one of the following species is not a Lewis base? Explain your ...

${\mathrm{H}}^{+},{\mathrm{Mg}}^{2+},{\mathrm{NH}}_3,{\mathrm{AlCl}}_3$ (iii) Which one of the following species is not a Lewis base? Explain your answer. ${\mathrm{H}}_2\mathrm{O},{\mathrm{F}}^{?},{\mathrm{BH}}_3,{\mathrm{OH}}^{?}$ In terms of the principle of hard and soft Lewis acids and bases explain the following observations. (i) The thermodynamic stability of the Group 1 oxides decreases in the following order. ${\mathrm{Li}}_2\mathrm{O}>{\mathrm{Na}}_2\mathrm{O}>{\mathrm{K}}_2\mathrm{O}>{\mathrm{Rb}}_2\mathrm{O}>{\mathrm{Cs}}_2\mathrm{O}$ (ii) The ability of the Group 15 Hydrides to act as proton $\left({\mathrm{H}}^{+}\right)$acceptors decreases in the following order. ${\mathrm{NH}}_3>{\mathrm{PH}}_3>{\mathrm{AsH}}_3$