Question

Given below are two statements Statement-I: Silicones have high thermal stability and high dielectric strength Statement-II: In silica Si-O bond enthalpy is very high

• A. Both statements I and II are correct
• B. Both statements I and II are not correct
• C. Statement I is correct, but statement II is not correct
• D. Statement I is not correct, but statement II is correct

Hint:

Silicone properties originate from strong Si-O bond. Stronger bond means higher thermal stability and excellent insulating behavior.

Answer 1

The Correct Option is A

Concept: Silicones are organosilicon polymers having repeating units involving silicon oxygen backbone. General structure: \[ (-Si-O-Si-O-)_{n} \] Their physical properties are governed by strength of Si-O bond. Bond enthalpy means bond strength. Higher bond enthalpy means stronger bond and greater thermal stability.

Step 1: Analyze Statement I. Silicones possess

• High thermal stability

• Water resistance

• Chemical inertness

• High dielectric strength
High dielectric strength means excellent electrical insulation. Thus statement I is true.

Step 2: Analyze Statement II. Silicon oxygen bond is extremely strong. Bond enthalpy approximately \[ Si-O\approx452kJ/mol \] This value is much greater than many ordinary covalent bonds. Therefore silica network is highly stable. Thus statement II is true.

Step 3: Establish relation between statements. Because Si-O bond is very strong, silicone polymers resist thermal decomposition. This directly explains high thermal stability. Hence statement II supports statement I. Both are correct. Therefore answer is \[ \boxed{A} \]