p-Block Elements-I: Choose the correct answer

Choose the correct answer:

1. An aqueous solution of borax is

a) neutral

b) acidic

c) basic

d) amphoteric

Solution:

2. Boric acid is an acid because its molecule

a) contains replaceable H+ ion

b) gives up a proton

c) combines with proton to form water molecule

d) accepts OH- from water ,releasing proton.

Solution:

B(OH)₃ + H₂O ↔ [B (OH)₄ + H⁺

3. Which among the following is not a borane?

a) B₂ H₆

b) B₃ H₆

c) B₄ H₁₀

d) none of these

Solution:

nido borane : B_nH_4+n

aracno borane : B_nH_6+n

B₃H₆ is not a borane

4. Which of the following metals has the largest abundance in the earth’s crust?

a) Aluminium

b) calcium

c) Magnesium

d) sodium

5. In diborane, the number of electrons that accounts for banana bonds is

a) six

b) two

c) four

d) three

Solution:

There are two 3c – 2e-bonding in the bridges account for 4 electrons.

6. The element that does not show catenation among the following p-block elements is

a) Carbon

b) silicon

c) Lead

d) germanium

7. Carbon atoms in fullerene with formula C₆₀ have

a) sp³ hybridised

b) sp hybridised

c) sp² hybridised

d) partially sp² and partially sp³ hybridised

8. Oxidation state of carbon in its hydrides

a) +4 

b) -4

c) +3

d) +2

Solution:

Example : CH₄₊ in which the oxidation state of carbon is +4

9. The basic structural unit of silicates is

a) ( SiO₃ )²⁻

b) ( SiO₄ )²⁻

c) ( SiO)⁻

d) ( SiO₄ )⁴⁻

10. The repeating unit in silicone is

a) SiO₂

Ans: b

11. Which of these is not a monomer for a high molecular mass silicone polymer?

a) Me₃SiCl

b) PhSiCl₃

c) MeSiCl₃

d) Me₂SiCl₂

12. Which of the following is not sp² hybridised?

a) Graphite

b) graphene

c) Fullerene

d) dry ice

Solution:

dry ice – solid CO₂ in which carbon is in sp hybridized state

13. The geometry at which carbon atom in diamond are bonded to each other is

a) Tetrahedral

b) hexagonal

c) Octahedral

d) none of these

14. Which of the following statements is not correct?

a) Beryl is a cyclic silicate

b) Mg₂SiO₄ is an orthosilicate

c) SiO₄ ⁴⁻is the basic structural unit of silicates

d) Feldspar is not aluminosilicate

15. AlF₃ is soluble in HF only in the presence of KF. It is due to the formation of

a) K₃ [ AlF₃H₃ ]

b) K₃ [ AlF₆ ]

c) AlH₃

d) K[ AlF₃H]

Solution:

AlF₃ + 3KF → K₃[AlF₆]

16. Match items in column - I with the items of column – II and assign the correct code.

a) A-2 , B-1 , C-4 , D-3

b) A-1 , B-2 , C-4 , D-3

c) A-1 , B-2 , C-4 , D-3

d) none of these

17. Duralumin is an alloy of

a) Cu,Mn

b) Cu,Al,Mg

c) Al,Mn

d) Al,Cu,Mn,Mg

Solution:

Al-95% , Cu-4% , Mn-0.5% , Mn-0.5%

18. Thermodynamically the most stable form of carbon is

a) Diamond

b) graphite

c) Fullerene

d) none of these

19. The compound that is used in nuclear reactors as protective shields and control rods is

a) Metal borides

b) metal oxides

c) Metal carbonates

d) metal carbide

20. The stability of +1 oxidation state increases in the sequence

a) Al < Ga < In < Tl

b) Tl < In < Ga < Al

c) In < Tl < Ga < Al

d) Ga< In < Al < Tl

Solution

stability of +1 oxidation state decreases down the group due to inert pair effect