#### 12th Standard Chemistry English Medium Solid State Reduced Syllabus Important Questions 2021

12th Standard

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Chemistry

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

Multiple Choice Questions

15 x 1 = 15
1. An ionic compound A x By crystallizes in fcc type crystal structure with B ions at the centre of each face and A ion occupying entre of the cube the correct formula of A x By is ___________

(a)

AB

(b)

AB3

(c)

A3B

(d)

A8B6

2. The ionic radii of A+ and B are 098X10-10 mand 1.81X10-10. m. the coordination number of each ion in AB is ____________

(a)

8

(b)

2

(c)

6

(d)

4

3. The yellow colour in NaCl crystal is due to __________

(a)

excitation of electrons in F centers

(b)

reflection of light from Cl- ion on the surface

(c)

refraction of light from Na+ ion

(d)

all of the above

4. Schottky defect in a crystal is observed when __________

(a)

unequal number of anions and anions are missing from the lattice

(b)

equal number of anions and anions are missing from the lattice

(c)

an ion leaves its normal site and occupies an interstitial site

(d)

no ion is missing from its lattice

5. Assertion: due to Frenkel defect, density of the crystalline solid decreases.
Reason: in Frenkel defect cation and anion leaves the crystal
Codes:
(a) Both assertion and reason are true and reason is the correct explanation of assertion
(b) Both assertion and reason are true but reason is not the correct explanation of assertion
(c) Assertion is true but reason is false
(d) Both assertion and reason are false

(a)

Both assertion and reason are true and reason is the correct explanation of assertion

(b)

Both assertion and reason are true but reason is not the correct explanation of assertion

(c)

Assertion is true but reason is false

(d)

Both assertion and reason are false

6. Which of the following is characteristic of ionic solids?

(a)

Very low value of electrical conductivity in the molten state

(b)

Brittie nature

(c)

Very strong forces of attractions

(d)

Anisotropic nature

7. A binary solid A+B- has a structure with B- ions constituting the lattice and A+ ions occupying 25% tetrahedral holes. Formula of the solid is

(a)

A2B

(b)

AB2

(c)

AB

(d)

AB4

8. Schottky defects contains

(a)

Cation vacancies only

(b)

Cation vacancies and interstitial cations

(c)

Equal number of cation and anion vacancies

(d)

Anion vacancies and interstitial anions

9. What is wrong about a.b.c.c. unit cell?

(a)

In addition to an atom at the centre of the body of the unit cell,there are 8 atoms at 8 differentcorners

(b)

$\frac{1}{8}$ atom at a corner of the unit cell

(c)

No. of atoms in the unit cellsis 2

(d)

The no. of atoms in the unit cells is 4

10. Which one of the following statements is wrong about Frenkel defect?

(a)

An ion occupies an interstitial position

(b)

Anion is much larger in size than the cation

(c)

The crystal remains neutral

(d)

Non-stoichiometric compound is formed

11. Examples of hydrogen bonded molecular solids

(a)

H2O

(b)

glucose

(c)

urea

(d)

all the above

12. The site labelled as 'X' in FCC arrangement is________

(a)

Face with 1/4 contribution

(b)

Edge with 1/4 contribution

(c)

Corner with 1/4 contribution

(d)

Tetrahedral void with 1/8 contribution

13. An example for Frenkel defect is __________.

(a)

NaCl

(b)

AgBr

(c)

CdCl

(d)

FeS

14. In a solid, the cation is missing from the lattice and is found in an interstital position. The defect is __________.

(a)

Metal excess

(b)

p type

(c)

Schottky

(d)

Frenkel

15. If electrical conductivity is found to be I same in all directions through a solid the substance is __________ solid and the property is called _________

(a)

crystalline, isotropy

(b)

amorphous, isotropy

(c)

crystalline, anisotropy

(d)

amorphous, isotropy

1. 2 Marks

10 x 2 = 20
16. Differentiate crystalline solids and amorphous solids.

17. classify the following solids
a. P4
b. Brass
c. diamond
d. NaCl
e. Iodine

18. What are point defects?

19. Why do solids have a definite volume?

20. Classify the following as amorphous or crystalline solids. Polyurethane, Naphthalene, Benzoic acid, Teflon, Potassium nitrate, Cellophane, Polyvinyl chloride, Fiber glass, Copper.

21. What type of stoichiometric defect is shown by ZnS.

22. Ionic solids conduct electricity in molten state but not in solid state. Explain.

23. What is point defect in crystals?

24. Why is FeS not formed in stoichiometric composition?

25. Frenkel defect is not show by alkali metal halides but silver halides do. Give reason.

1. 3 Marks

10 x 3 = 30
26. Explain Schottky defect.

27. Write short note on metal excess and metal deficiency defect with an example

28. Why ionic crystals are hard and brittle?

29. Experiment shows that Nickel oxide has the formula Ni0.96.O1.00 What fraction of Nickel exists as of Ni2+ and Ni3+ ions?

30. Silver crystallines in fcc lattice. If edge length of the cell is 4.07 x 10-8 em and density is 10.5 g cm-3. Calculate the atomic mass of silver

31. Why are solids incompressible?

32. Classify the following solids in different categories based on the nature of intermolecular force operating in them: Potassium sulphate, tin, benzene, urea, ammonia, water, zinc sulphide, graphite, rubidium, argon, silicon carbide.

33. Examine the given defective crystal:

 X+ Y- X+ Y- X+ Y- O X+ X+ X+ O X+ Y- X+ Y- X+ Y-

(i) Is the above defect stoichiometric or non-stoichiometric?
(ii) What are such defects called? Give an example of the compound which shows this type of defect.

34. Sketch the
(a) Simple cubic
(b) face-centred
cubic and
(c) body centred cubic lattices.

35. Write the properties of ionic crystals.

1. 5 Marks

7 x 5 = 35
36. if NaCl is doped with 10-2 mol percentage of strontium chloride, what is the concentration of cation vacancy

37. Atoms X and Y form bcc crystalline structure. Atom X is present at the corners of the cube and Y is at the centre of the cube. What is the formula of the compound?

38. Write a note on Frenkel defect.

39. Ionic solids, which have anionic vacancies due to metal excess defect, develop colour. Explain with the help of a suitable example.

40. What are the general characteristics of solids?

41. How can you determine the atomic mass of an unknown metal if you know its density and the dimension of its unit cell? Explain.

42. What are stoichiometric defects in ionic solids? Explain