Chemistry Class-11: Chapter –11. The p-Block Elements Part – 6

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In the following questions a statement of Assertion (A) followed by a statement of Reason (R) is given. Choose the correct option out of the choices given below each question.

Question: 39

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.

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

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

(iii) Both A and R are not correct

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

Answer: (i)

Question: 40.

Assertion (A): Silicones are water repelling in nature.

Reason (R): Silicones are organ silicon polymers, which have as repeating unit. (i) A and R both are correct and R is the correct explanation of A.

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

(iii) A and R both are not true.

(iv) A is not true but R is true.

Answer: (ii)

VI. Long Answer Type

Question: 41

Describe the general trends in the following properties of the elements in Groups 13 and 14.

(i) Atomic size

(ii) Ionization enthalpy

(iii) Metallic character

(iv) Oxidation states

(v) Nature of halides

Answer:

Question: 42.

Account for the following observations:

(i) is a Lewis acid

(ii) Though fluorine is more electronegative than chlorine yet is a weaker Lewis acid than

(iii) is a stronger oxidising agent than

(iv) The oxidation state of thallium is more stable than its state.

Answer:

Question: 43

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

Answer:

Question: 44

Three pairs of compounds are given below. Identify that compound in each of the pairs which has group 13 element in more stable oxidation state. Give reason for your choice. State the nature of bonding also.

(i)

(ii)

(iii)

Answer:

Question: 45

exists as monomer whereas is dimerised through halogen bridging. Give reason. Explain the structure of the dimer of also

Answer:

[Hint: Absence of d-orbitals in boron.]

Question: 46

Boron fluoride exists as but boron hydride doesn’t exist as . Give reason. In which form does it exist? Explain its structure

Answer:

Question: 47

(i) What are silicones? State the uses of silicones.

(ii) What are boranes? Give chemical equation for the preparation of diborane

Answer:

Question: 48

A compound (A) of boron reacts with to give an adduct (B) which on hydrolysis gives a compound (C) and hydrogen gas. Compound (C) is an acid. Identify the compounds A, B and C. Give the reactions involved.

Answer:

Question: 49

A nonmetallic element of group 13, used in making bullet proof vests is extremely hard solid of black colour. It can exist in many allotropic forms and has unusually high melting point. Its trifluoride acts as Lewis acid towards ammonia. The element exhibits maximum covalency of four. Identify the element and write the reaction of its trifluoride with ammonia. Explain why does the trifluoride act as a Lewis acid.

Answer:

Question: 50

A tetravalent element forms monoxide and dioxide with oxygen. When air is passed over heated element , producer gas is obtained. Monoxide of the element is a powerful reducing agent and reduces ferric oxide to iron. Identify the element and write formulas of its monoxide and dioxide. Write chemical equations for the formation of producer gas and reduction of ferric oxide with the monoxide.

Answer:

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