(a) When methyl chloride reacts with silicon in the presence of copper as a catalyst at a temperature 573 K various types of methyl substituted chlorosilane of formula $\mathrm{MeSiCl}_3, \mathrm{Me}_2\mathrm{SiCl}_2, \mathrm{Me}_3\mathrm{SiCl}$ with small amount of $\mathrm{Me}_4\mathrm{Si}$ are formed. $2\mathrm{CH}_3\mathrm{Cl} + \mathrm{Si}$ $\xrightarrow[573\,\text{K}]{\text{Cu powder}}$ $(\mathrm{CH}_3)\mathrm{SiCl}_3+(\mathrm{CH}_3)_2\mathrm{SiCl}_2$ + $(\mathrm{CH}_3)_3\mathrm{SiCl} + (\mathrm{CH}_3)_4\mathrm{Si}$ (b) When silicon dioxide is treated with HF, silicon tetrafluoride is formed. $\mathrm{SiO}_2 + 4\mathrm{HF}$ → $\mathrm{SiF}_4 + 2\mathrm{H}_2\mathrm{O}$ (c) CO is a powerful reducing agent, it reduces ZnO to Zn. $\mathrm{CO}_{\text{(g)}} + \mathrm{ZnO}_{\text{(s)}}$ $\xrightarrow[]{{\Delta}}$ $\mathrm{Zn}_{\text{(s)}} + \mathrm{CO}_{2\text{(g)}}$ ↑ (d) Aluminium reacts with aqueous alkali and liberates hydrogen gas. $2\mathrm{Al}_{\text{(s)}} + 2\mathrm{NaOH}_{\text{(aq)}} + 6\mathrm{H}_2\mathrm{O}_{\text{(l)}}$ → $2\mathrm{Na}^{+}[\mathrm{Al}(\mathrm{OH})_4]^{-}_{\text{(aq)}}+3\mathrm{H}_{2\text{(g)}}$ ↑