Assertion (A): If aluminium atoms replace a few silicon atoms in three dimensional network of silicon dioxide, the overall structure acquires a negative charge.

Reason (R): Aluminium is trivalent while silicon is tetravalent.

(A) Both A and R are true and R is the correct explanation of A.

(B) Both A and R are true but R is not the correct explanation of A.

(C) Both A and R are not correct.

(D) A is not correct but R is correct.

This is a Assertion and Reason Type Questions as classified in NCERT Exemplar

(B)

Silicones are a class of silicon polymers that contain the repeating unit (-R 2 SiO-). Silicones are water repellent in nature because they are surrounded by non-polar alkyl groups, so A and R are both correct, but R is not the correct explanation of A.

This is a Matching Type Questions as classified in NCERT Exemplar

(i)→ (b), (ii) → (c), (iii) → (b), (iv) → (a) (v)→ (b) (vi)→ (c)

This is a Matching Type Questions as classified in NCERT Exemplar

(i)→ (c) (ii)→ (d) (iii)→ (a) (iv)→ (e) (v)→ (b)

This is a Matching Type Questions as classified in NCERT Exemplar

(i)- (e), (ii)- (c), (iii)- (d), (iv)- (a) & (b)

This is a Multiple Choice Questions as classified in NCERT Exemplar

(B) & (D)

The following is the resonance structure of CO₂.