Explain CO₂ is a gas while SiO₂ is solid.

Rationalise the given statements and give chemical reactions:

(a) Lead (II) chloride reacts with Cl₂ to give PbCl₄.

(b) Lead (IV) chloride is highly unstable towards heat.

(c) Lead is known not to form an iodide PbI₄.

Why PbCl₄ exists whereas PbBr₄ and Pbl₄ do not? Explain.

165.

Classify following oxides as neutral, acidic, basic or amphoteric:
CO, B₂O₃, SiO₂, CO₂, A1₂O₃, PbO₂, Tl₂O₃. 

What are silicones? How are these prepared? Give their uses.
Or
What are silicones? Give methods for the preparation of different types of silicones. 

If the starting material for the manufacture of silicones is RSiCl₃, write the structure of the product formed. 

What are the applications of silicones in technology?
Or
Mention some uses of silicones.

Explain the following reactions:
Silicon is heated with methyl chloride at high temperature in the presence of copper.

Explain the following reactions:
Silicon dioxide is treated with hydrogen fluoride.