Chemistry Class 11 NCERT Solutions: Chapter 11 the P Block Elements Part 5 (For CBSE, ICSE, IAS, NET, NRA 2022)

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Q: 20. What happens when

(A) Borax is heated strongly

(B) Boric acid is added to water

(C) Aluminium is treated with dilute

(D) is reacted with ammonia?

Answer:

(A) When heated, borax undergoes various transitions. It first lises water moecules and swells. Then, it turns into a transparent liquid, solidifying to form a glass – like material called borax bead.

(B) When boric acid is added to water, it accepts electrons from ion.

(C) Al reacts with dilute to form sodium tetrahydroxoaluminate (III) . Hydrogen gas is liberated in the process.

(D) (a Lewis acid) reacts with (a Lewis base) to form an adduct. This results in a complete octet around B in .

Q: 21. 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) is heated with ;

(D) Hydrated alumina is treated with aqueous solution.

Answer:

(A) When silicon reactes with methyl chloride in the presence of copper (catalyst) and at a temperature of about 537 K, a class organosilicon polymers called methyl- substituted chlorosilanes ) are formed

Q_21_A_Silicon is Heated with Methyl Chloride at High Temper …

(B) When silicon dioxide is heated with hydrogen fluoride , it forms silicon tetrafluoride . Usually, the 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 formed in this reaction can further react with HF to form hydrofluorosilicic acid

(C) When reacts with , it reduces to . 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.

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