Write down the reaction equations that can be used to obtain: a) a soluble base; b) practically insoluble base.

a) Soluble base:
Soluble bases can be obtained by the interaction of active metals and their oxides with water, therefore:
2Li + 2H2O = 2LiOH + H2 (substitution)
Li2O + H2O = 2LiOH (compound), lithium hydroxide
BaO + H2O = Ba (OH) 2 (compound), barium hydroxide.
b) Practically insoluble base:
Insoluble bases can be obtained by the interaction of salts and soluble bases, therefore:
FeCl3 + NaOH = Fe (OH) 3 + 3NaCl (exchange)
CuSO4 + 2LiOH = Cu (OH) 2 + Li2SO4 (exchange)
Pb (NO3) 2 + 2KOH = Pb (OH) 2 + 2KNO3 (exchange)