(i) Mg burns with dazzling brilliance evolving a lot of heat. 2Mg + $\mathrm{O}_2$ → 2MgO and 3Mg + $\mathrm{N}_2$ → $\mathrm{Mg}_3\mathrm{N}_2$ (ii) When quicklime (CaO) is heated with silica, it forms calcium silicate $(\mathrm{CaSiO}_3)$. CaO + $\mathrm{SiO}_2$ → $\mathrm{CaSiO}_3$. (iii) Chlorine reacts with slaked lime to give bleaching powder. $\underset{\text{Slaked lime}}{2\mathrm{Ca(OH)_{2(s)}}} + 2\mathrm{Cl}_{2(g)}$ → $\underset{\text{Bleaching powder}}{\mathrm{Ca(OCl)_2+CaCl_2}} + 2\mathrm{H_2O}$ (iv) When calcium nitrate is heated, it decomposes to form calcium oxide, nitrogen dioxide and oxygen. $2\mathrm{Ca(NO_3)_2}$ → $2\mathrm{CaO} + 4\mathrm{NO}_2 + \mathrm{O}_2$