Class 11 Chemistry The p Block Element Exam Questions

LEVEL – 1

1. Why is boron used in nuclear reactions?

Ans: Because Boron can absorb neutrons .

2. By giving a balanced equation show how B(OH)_₃ behaves as an acid in water.

3. Name the element of group 14 which exhibits maximum tendency for catenation.

Ans: Carbon

4. What is the basic building unit of all SILICATES?

Ans: SiO⁴₄⁻

5. What happens when NaBH₄ reacts with iodine ?

Ans: 

6. What is producer gas?

Ans: Producer gas is a mixture of CO and N₂ in the ratio 2:1

7. What happens when BORIC acid is heated?

8 .Ga has high ionization enthalpy than Al. Explain.

Ans: Due to poor shielding effect of d-electrons in Ga effective nuclear charge increases as compared to Al thus IE is higher than Al.

9.What are Fullerene ? How they were prepared

Ans: Fullerene are the allotropes of carbon Its structure is like a soccer ball. They were prepared by heating graphite in electric arc in presence of inert gases He or Ar.

LEVEL – 2

1. Give biological importance of Ca and Mg.

Ans: Calcium and magnesium ions are essential for the transmission of impulses along nerve fibres. Magnesium is present in chlorophyll in green plants, calcium ions also regulates the beating of the heart.

2. Name the chief factors responsible for anomalous behaviour of lithium.

Ans: (i) Small size atom and ion,

(ii) High ionization enthalpy

(iii) Absence of d-orbital in its Valence shell.

3. Describe two similarities and two dissimilarities between B &Al.

Ans: Similarities: (i) Both have same number of valence electrons. (ii) Both have similar electronic configuration. Dissimilarities: (i) B is a non - metal whereas Al is a metal. (ii) B forms acidic oxides whereas Al forms amphoteric oxides.

4. Give reason for the following observations.

(a) The tendency for catenation decreases down the group.

(b) The decreasing stability of +3 oxidations state with increasing atomic number in group 13.

(c) PbO₂ IS a stronger oxidizing agent than SnO₂.

(d) Molten aluminium bromide is a poor conductor of electricity.

Ans: (a) It is due to decrease in bond dissociation energy which is due to increase in atomic size

(b) It is due to Inert Pair Effect.

(c) PbO₂ is stronger oxidizing agent than SnO₂ because Pb²⁺ is more stable than Pb⁴⁺ whereasSn⁴⁺ is more stable than Sn²⁺.

(d) Molten AlBr₃ is poor conductor of electricity because it is covalent compound.

LEVEL – 3

1. Silanes are few in number where as alkanesare large in number .Explain.

Ans: Carbon has the maximum tendency for catenation due to stronger C-C bonds as aresult it forms a large number of alkanes Silicon on other hand due to weaker Si-Si bonds has much lesser tendency for catenation and hence forms only a few silanes.

2. What are SILICONES?

Ans: SILICONES are the synthetic organo-silicon polymers having general formulae ( R₂ SiO )n in which R = alkyl ( methyl, ethyl or phenyl )

3. What are Zeolites?

Ans: Zeolites are 3D silicates in which the Si atoms are replaced by Al3⁺ions and negative charge is balanced by cations such as Na⁺, K⁺,Ca²⁺ ( NaAlSi₂O₆H₂O)

4. When aqueous solution of borax is acidified with hydrochloric acid,a white crystalline solid is formed which is soapy in touch .Is this solid acidic or basic in nature? Explain.

Ans: When an aqueous solution of borax is acidified with HCl boric acid is formed

Na₂B₄O₇ + 2 HCl + 5 H₂O → 2NaCl + 4 H₃BO₃ (BORIC ACID)

Boric acid is not a proticacid it does not give H⁺ ion accepts a pair of electrons and acts as a Lewis acid

5 .Out of CCl₄ and SiCl₄ which one reacts with water? Ans: Due to presence of d-orbitals in Si, SiCl₄ reacts with water but due to the absence of d-orbitals in C , CCl₄ does not react with water. 6. Which compound is known as inorganic benzene?

Ans: Borazine ( or borazole ) B₂H₆.2NH₃ when heated it gives B₃N₃H₆( Borazine) because of its structure is very similar to C₆H₆ ( Benzene) and hence BORAZINE (OR BORAZOLE ) is known as inorganic benzene.