#### 12th Standard Chemistry English Medium P - Block Elements - I Reduced Syllabus Important Questions With Answer Key 2021

12th Standard

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Chemistry

Time : 01:00:00 Hrs
Total Marks : 100

Multiple Choice Questions

15 x 1 = 15
1. 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.

2. Oxidation state of carbon in its hydrides ___________

(a)

+4

(b)

-4

(c)

+3

(d)

+2

3. The basic structural unit of silicates is __________

(a)

$\left( SiO_{ 3 } \right) ^{ 2- }$

(b)

$\left( SiO_{ 4 } \right) ^{ 2- }$

(c)

$\left( Sio \right) ^{ - }$

(d)

$\left( SiO_{ 4 } \right) ^{ 4- }$

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

(a)

Me3SiCl

(b)

PhSiCl3

(c)

MeSiCl3

(d)

Me2SiCl2

5. Which of the following statements is not correct?

(a)

Beryl is a cyclic silicate

(b)

Mg2SiO4 is an orthosilicate

(c)

SiO44−i the basic structural unit of silicates

(d)

Feldspar is not aluminosilicate

6. Duralumin is an alloy of ___________

(a)

Cu,Mn

(b)

Cu,Al,Mg

(c)

Al,Mn

(d)

Al,Cu,Mn,Mg

7. Thermodynamically the most stable form of carbon is

(a)

Diamond

(b)

graphite

(c)

Fullerene

(d)

none of these

8. 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

9. Which one of the following compounds has similar structure to that of graphite?

(a)

Boron nitride

(b)

Boron Carbide

(c)

Aluminium Carbide

(d)

Aluminium Oxide

10. Identify the electron - deficient species

(a)

(BH3)2

(b)

(SiH3)2

(c)

PH3

(d)

(CH3)2

11. Boron compounds behave as Lewis acid, because of their

(a)

ionisation property

(b)

acidic nature

(c)

covalent nature

(d)

electron deficient nature

12. On moving down the group 13, density ______

(a)

decreases

(b)

increases

(c)

First decreases then increases

(d)

remains same

13. Elements of group 13 mainly form covalent compounds because ______

(a)

small size

(b)

electro negativity values are high

(c)

ionization energy is very high

(d)

both (a) and (c)

14. Allotropy is due to ______

(a)

difference in chemical properties

(b)

difference in the number of atoms in the molecules

(c)

difference in the arrangement of atoms in the molecules in the crystal

(d)

None of these

15. Borax is _______

(a)

Na2[B4O5(OH)4).8H2O

(b)

Na2[B4O5(OH)6).7H2O

(c)

Na2[B4O3(OH)8].6H2O

(d)

Na2[B4O2(OH)10).5H2O

16. 2 Marks

10 x 2 = 20
17. Describe briefly allotropism in p- block elements with specific reference to carbon

18. What is catenation ? describe briefly the catenation property of carbon

19. Give the structure of CO and CO2.

20. How is boric acid extracted from borax?

21. Mention the physical properties of boranes.

22. What is burnt alum?

23. What is water gas equilibrium?

24. What are the uses of silicon tetra chloride?

25. What is inert pair effect?

26. Name the two important ores of Boron.

27. 3 Marks

10 x 3 = 30
28. Give the uses of silicones

29. Describe the structure of diborane

30. Write a short note on hydroboration

31. Give one example for each of the following
(i) icosogens
(ii) tetragen
(iii) prictogen
(iv) chalcogen

32. What happens to boranes at high temperatures?

33. How is aluminum chloride prepared from aluminum?

34. Describe the structure of graphite.

35. Describe the structure of carbon nanotubes.

36. Describe the structure of graphene.

37. Account for the following:
(i) CO is used in the extraction of metals.
(ii) CO is poisonous
(iii) CO2 is used in referigeration

38. 5 Marks

7 x 5 = 35
39. How will you identify borate radical?

40. How will you convert boric acid to boron nitride?

41. A hydride of 2nd period alkali metal (A) on reaction with compound of Boron (B) to give a reducing agent (C). identify A , B and C.

42. CO is a reducing agent . justify with an example.

43. What are the various methods by which carbon-di-oxide is prepared?

44. How are silicates classified? Give an example for each type of silicate.

45. Distinguish between diamond and graphite.