CBSE Class 11 Chemistry VBQs P Block Elements

Question. The correct order of atomic radii in group 13 elements is
(a) B < Al < In < Ga < Tl
(b) B < Al < Ga < In < Tl
(c) B < Ga < Al < Tl < In
(d) B < Ga < Al < In < Tl 
Answer. D

Question. AlF₃ is soluble in HF only in presence of KF. It is due to the formation of
(a) K₃[AlF₃H₃]
(b) K₃[AlF₆]
(c) AlH₃
(d) K[AlF₃H]
Answer. B

Question. The stability of +1 oxidation state among Al, Ga, In and Tl increases in the sequence
(a) Al < Ga < In < Tl
(b) Tl < In < Ga < Al
(c) In < Tl < Ga < Al
(d) Ga < In < Al < Tl
Answer. A

Question. Aluminium(III) chloride forms a dimer because aluminium
(a) belongs to 3rd group
(b) can have higher coordination number
(c) cannot form a trimer
(d) has high ionization energy. 
Answer. B

Question. Which one of the following elements is unable to form MF₆^3– ion?
(a) Ga
(b) Al
(c) B
(d) In 
Answer. C

Question. The tendency of BF₃, BCl₃ and BBr₃ to behave as Lewis acid decreases in the sequence
(a) BCl₃ > BF₃ > BBr₃
(b) BBr₃ > BCl₃ > BF₃
(c) BBr₃ > BF₃ > BCl₃
(d) BF₃ > BCl₃ > BBr₃ 
Answer. B

Question. Boron compounds behave as Lewis acids, because of their
(a) ionisation property
(b) electron deficient nature
(c) acidic nature
(d) covalent nature. 
Answer. B

Question. Boric acid is an acid because its molecule
(a) contains replaceable H⁺ ion
(b) gives up a proton
(c) accepts OH– from water releasing proton
(d) combines with proton from water, molecule.
Answer. C

Question. Which of the following structure is similar to graphite?
(a) B4C
(b) B₂H₆
(c) BN
(d) B 
Answer. C

Question. The type of hybridisation of boron in diborane is
(a) sp³-hybridisation
(b) sp²-hybridisation
(c) sp-hybridisation
(d) sp³d²-hybridisation.
Answer. A

Question. Which of the following statements about H₃BO₃ is not correct?
(a) It has a layer structure in which planar BO₃ units are joined by hydrogen bonds.
(b) It does not act as proton donor but acts as a Lewis acid by accepting hydroxyl ion.
(c) It is a strong tribasic acid.
(d) It is prepared by acidifying an aqueous solution of borax.
Answer. C

Question. Which of the following is incorrect statement ?
(a) SnF₄ is ionic in nature.
(b) PbF₄ is covalent in nature.
(c) SiCl₄ is easily hydrolysed.
(d) GeX₄ (X = F, Cl, Br, I) is more stable than GeX₂.
Answer. B

Question. Which of the following species is not stable?
(a) [SiCl₆]^2–
(b) [SiF_6]^2–
(c) [GeCl_6]^2–
(d) [Sn(OH)_6]^2–
Answer. A

Question. It is because of inability of ns² electrons of the valence shell to participate in bonding that
(a) Sn²⁺ is oxidising while Pb⁴⁺ is reducing
(b) Sn²⁺ and Pb²⁺ are both oxidising and reducing
(c) Sn⁴⁺ is reducing while Pb⁴⁺+ is oxidising
(d) Sn²⁺ is reducing while Pb⁴⁺ is oxidising.
Answer. D

Question. Which of the following oxidation states are the most characteristic for lead and tin respectively?
(a) +2, +4
(b) +4, +4
(c) +2, +2
(d) +4, +2 
Answer. A

Question. Carbon and silicon belong to (IV) group. The maximum coordination number of carbon in commonly occurring compounds is 4, whereas that of silicon is 6. This is due to
(a) availability of low lying d-orbitals in silicon
(b) large size of silicon
(c) more electropositive nature of silicon
(d) both (b) and (c). 
Answer. A

Question. Which of the following does not show electrical conduction?
(a) Diamond
(b) Graphite
(c) Potassium
(d) Sodium 
Answer. A

Question. Percentage of lead in lead pencil is
(a) 80
(b) 20
(c) zero
(d) 70 
Answer. C

Question. In graphite, electrons are
(a) localised on each C-atom
(b) localised on every third C-atom
(c) spread out between the structure
(d) present in antibonding orbital. 
Answer. C

Question. Which of the following types of forces bind together the carbon atoms in diamond?
(a) Ionic
(b) Covalent
(c) Dipolar
(d) van der Waals 
Answer. B

Question. Which of the following is an insulator?
(a) Graphite
(b) Aluminium
(c) Diamond
(d) Silicon 
Answer. C

Question. Identify the correct statements from the following :
(A) CO_2(g) is used as refrigerant for ice-cream and frozen food.
(B) The structure of C60 contains twelve six carbon rings and twenty five carbon rings.
(C) ZSM-5, a type of zeolite, is used to convert alcohols into gasoline.
(D) CO is colourless and odourless gas.
(a) (A), (B) and (C) only
(b) (A) and (C) only
(c) (B) and (C) only
(d) (C) and (D) only
Answer. D

Question. Which of the following compounds is used in cosmetic surgery?
(a) Silica
(b) Silicates
(c) Silicones
(d) Zeolites
Answer. C

Question. Which of these is not a monomer for a high molecular mass silicone polymer?
(a) Me₃SiCl
(b) PhSiCl₃
(c) MeSiCl₃
(d) Me₂SiCl₂
Answer. A

Question. The basic structural unit of silicates is
(a) SiO₃^2–
(b) SiO₄^2–
(c) SiO^–
(d) SiO₄^4– 
Answer. D

Question. Which statement is wrong?
(a) Beryl is an example of cyclic silicate.
(b) Mg₂SiO₄ is orthosilicate.
(c) Basic structural unit in silicates is the SiO₄ tetrahedron.
(d) Feldspars are not aluminosilicates.
Answer. D

Question. Name the two types of the structure of silicate in which one oxygen atom of [SiO₄]^4– is shared?
(a) Linear chain silicate
(b) Sheet silicate
(c) Pyrosilicate
(d) Three dimensional
Answer. C

Question. The straight chain polymer is formed by
(a) hydrolysis of CH₃SiCl₃ followed by condensation polymerisation
(b) hydrolysis of (CH₃)₄Si by addition polymerisation
(c) hydrolysis of (CH₃)₂SiCl₂ followed by condensation polymerisation
(d) hydrolysis of (CH₃)₃SiCl followed by condensation polymerisation. 
Answer. C

Question. Which of the following anions is present in the chain structure of silicates?
(a) (Si₂O₅^2–)_n
(b) (SiO₃^2–)_n
(c) SiO₄^4–
(d) Si₂O₇^6– 
Answer. B

Question. Which one of the following statements about the zeolite is false?
(a) They are used as cation exchangers.
(b) They have open structure which enables them to take up small molecules.
(c) Zeolites are aluminosilicates having three dimensional network.
(d) Some of the SiO₄^4– units are replaced by AlO₄^5–and AlO₆^9– ions in zeolites. 
Answer. D

Question. The substance used as a smoke screen in warfare is
(a) SiCl₄
(b) PH₃
(c) PCl₅
(d) acetylene
Answer. A

Question. One of the elements of group 13 was not known at that time when Mendeleev gave his periodic table. This element has some interesting properties much different from other elements of this group.

Now answer the following questions:

(i) Name the element which was not known at Mendeleev’s time.
Answer: Gallium

(ii) Mention its interesting properties.
Answer: It can melt at 303 K but it does not boil up to 2676 K.

(iii) Give its one use.
Answer: Used as semi-conductor.

Question. Kevlar is a nylon obtained by condensation polymerisation of 1,4- diaminobenzene and 1,4- benzenedicarboxylic acid. Its fibre is five times stronger than steel and hence are used for making bullet- proof vests. There are two compounds of boron which are also used for making bullet-proof vests.

Now answer the following questions:

(i) Name the two compounds of boron used for making bullet-proof vests and how are they prepared?
Answer: Boron nitride (BN) and Boron carbide (B₄C)​​​​​​
B₂O_3(s) + 2NH₃à ₂ BN _(s) + 3H₂O _(g) (At 1173 K)
2 B₂O_3(s) + 7 C _(s) –Electric furnace --> B₄C _(s) + 6CO _(g) (At 1873 K)

(ii) What are the advantages of using boron based compounds over Kevlar?
Answer:  Boron has high ability to absorb neutrons and hence these two boron compounds can act as protective shield against radioactive radiations.

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