Question

Correct statements among (a) to (d) regarding silicones are:
a) They are polymers which hydrophobic character
b) They are biocompatible.
c) In general, they have thermal stability and low dielectric strength.
d) Usually, they are resistant to oxidation and used as greases.
A.(a), (b), and (c) only.
B.(a), (b), (c) and (d)
C.(a), and (b) only
D.(a), (b), and (d) only.

Answer 1

Hint: Silicones are compounds having a silicon-oxygen backbone with organic substituents attached to silicon through $C - Si$ bonds. The physical properties of silicones are similar to those of alkanes, despite the presence of polar chains.

Complete step by step answer:
> The presence of different organic substituents to the $Si - O$ framework makes them water repellent and hence these polymers have hydrophobic character. Due to the hydrophobic nature, these silicones are dissolved in a mixture of wax and an organic solvent and can be used in paints and waterproofing fabrics, paper, and leather. 

> Silicones are non-irritant and non-toxic materials due to their low reactivity that makes them bio-compatible. They are used in a number of substances such as Hip implants, pacemakers, artificial heart valves, etc.

> The silicones are thermally stable compounds and their stability comes from the high amount of energy required to break the $Si - O$ and $Si - Alkyl$ bonds. They also have high dielectric constant and that is why they are good insulators. So, this statement is incorrect.
> Silicones are surrounded on all sides by non-polar molecules and hence they are resistant to oxidation.

So, the correct answer is option (D).

Note:
-Mostly used silicones are those with methyl groups as the substituent.
-The properties of the silicones, such as solubility in organic solvents, water repellency, and flexibility can be altered by changing the organic substituents attached to the Si-atom.
-They can also be used as semiconductors.