Question

Explain the following reactions 

(a)Silicon is heated with methyl chloride at high temperature in the presence of copper; 

(b)Silicon dioxide is treated with hydrogen fluoride; 

(c) CO is heated with ZnO; 

(d)Hydrated alumina is treated with aqueous NaOH solution. 

Answer 1

(a) When silicon reacts with methyl chloride in the presence of copper (catalyst) and at a temperature of about 537 K, a class of organosilicon polymers called methylsubstituted chlorosilanes (MeSiCl₃, Me₂SiCl₂, Me₃SiCl, and Me₄Si) are formed. 

(b) When silicon dioxide (SiO₂) is heated with hydrogen fluoride (HF), it forms silicon tetrafluoride (SiF₄). Usually, the Si–O bond is a strong bond and it resists any attack by halogens and most acids, even at a high temperature. However, it is attacked by HF. 

The SiF₄ formed in this reaction can further react with HF to form hydrofluorosilicic acid. 

(c) When CO reacts with ZnO, it reduces ZnO to Zn. CO acts as a reducing agent. 

(d) When hydrated alumina is added to sodium hydroxide, the former dissolves in the latter because of the formation of sodium meta-aluminate.