(a) Magnesium carbonate is prepared by treating magnesium chloride with sodium hydrogencarbonate.
MgCl2 + NaHCO3 → MgCO3 + 2NaCl + H2O + CO2
(b) Lead carbonate is prepared by double displacement reaction between lead nitrate and potassium carbonate.
Pb(NO3)2 + K2CO3 → PbCO3 + 2KNO3
(c) Sodium bicarbonate is prepared by treating solution of sodium carbonate in water with carbon dioxide.
Na2CO3 + CO2 + H2O → 2NaHCO3