Explain the following reactions (a) Silicon is heated with methyl chloride at high temperature in the presence of copper. (b) Silicon dioxideis treated with hydrogenfluoride. (c ) CO is heatedwith ZnO. (d) Hydrated alumina is treated with aqueous NaOH solution.

Explain the following reactions (a) Silicon is heated with methyl chlo

1.	Explain the following reactions (a) Silicon is heated with methyl chloride at high temperature in the presence of copper. (b) Silicon dioxideis treated with hydrogenfluoride. (c ) CO is heatedwith ZnO. (d) Hydrated alumina is treated with aqueous NaOH solution.
Answer» Solution :(a) A mixture of mono-, di - and trimethlychlorosilanes along with a small amount of tetramethylsation is formed. `underset(" Methyl chloride ")(CH_(3)CL) + SI underset(570K)overset("Cu powder ") rarr CH_(3)SiCl_(3) + (CH_(3))_(2)SiCl_(2) + (CH_(3))_(3)SiCl + (CH_(3))_(4)Si` (b) The INITIALLY formed silicontetrafluoride dissolves in `HF` to form hydrofluorosilicic acid `SiO_(2) + 4 HF rarr SiF_(4) + 2H_(2)O` , `SiF_(4) + 2HF rarr H_(2)SiF_(6)` (c ) `ZNO` is reducedto zinc metal. `ZnO + CO rarr Zn + CO_(2)` (d) Alumina dissolves to form sodium meta-aluminate `underset("or Bauxite ")underset(" Hydrated aluminia ")(AlO_(3).2H_(2)O(s)) + 2NaOH(aq) overset("Heat")rarrunderset(" Sod. meta-aluminate ")(2NaAlO_(2)) + 3H_(2)O` or `Al_(2)O_(3).2H_(2)O(l) + 2NaOH (aq) + H_(2)O(l) overset("Heat")rarrunderset(" Sod. tetrahydroxoaluminate (III)")(2Na[Al(OH)_(4)](aq))`