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#### Public Model Question Paper Part-II 2019 - 2020

12th Standard EM

Reg.No. :
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Chemistry

Time : 02:45:00 Hrs
Total Marks : 70

Part I

Choose the most suitable answer from the given four alternatives and write the option code with the corresponding answer.

15 x 1 = 15
1. Name the process by which elements such as germanium, silicon and galium are refined.

(a)

Vapour phase method

(b)

Electrolytic refining

(c)

Zone refining

(d)

Van-Arkel method

2. An aqueous solution of borax is

(a)

neutral

(b)

acidic

(c)

basic

(d)

amphoteric

3. Pick the wrong one among the following

(a)

F2 - Yellow

(b)

Br2 - Red

(c)

Cl2 - Colourless

(d)

I2- Violet

4. Which one of the following ions has the same number of unpaired electrons as present in V3+?

(a)

Ti3+

(b)

Fe3+

(c)

Ni2+

(d)

Cr3+

5. A complex in which the oxidation number of the metal is zero is

(a)

K4[fe(CN)6]

(b)

[Fe(CN)3(NH3)5]

(c)

[Fe(CO)5]

(d)

both (b) and (c)

6. The number of close neighbours in a body centred cubic lattice of identifical spheres is

(a)

6

(b)

4

(c)

12

(d)

8

7. The half life period of a radioactive element is 140 days. After 560 days , 1 g of element will be reduced to

(a)

$\left( \cfrac { 1 }{ 2 } \right) g$

(b)

$\left( \cfrac { 1 }{ 4 } \right) g$

(c)

$\left( \cfrac { 1 }{ 8 } \right) g$

(d)

$\left( \cfrac { 1 }{ 16 } \right) g$

8. Which of these is not likely to act as lewis base?

(a)

BF3

(b)

PF3

(c)

CO

(d)

F

9. The hydrogen ion concentration of a buffer solution consisting of a weak acid and its salt is given by

(a)

$[{ H }^{ + }]={ K }_{ a }\frac { [Acid] }{ [Salt] }$

(b)

$[{ H }^{ + }]={ K }_{ a }[Salt]$

(c)

$[{ H }^{ + }]={ K }_{ a }[Salt]$

(d)

$[{ H }^{ + }]={ K }_{ a }\frac { [Acid] }{ [Salt] }$

10. The overall reaction that takes place in an electrochemical cell is

(a)

oxidation

(b)

reduction

(c)

decomposition

(d)

redox reaction

11. Which one of the following is correctly matched?

(a)

Emulsion - Smoke

(b)

Gel - butter

(c)

foam - Mist

(d)

whipped cream - sol

12. The IUPAC name for isobutyl alcohol is _______

(a)

2-methyl-l-propanol

(b)

2-methyl-l-butanol

(c)

2,2-dimethyl-2-propanol

(d)

1,1-dimethyl- 2-butanol

13. Which of the following represents the correct order of acidity in the given compounds

(a)

FCH2COOH > CH3COOH > BrCH2COOH > ClCH2COOH

(b)

FCH2COOH > ClCH2COOH > BrCH2COOH > CH2COOH

(c)

CH3COOH > ClCH2COOH > FCH2COOH > Br-CH2COOH

(d)

Cl CH2COOH > CH3COOH > BrCH2COOH > ICH2COOH

14. Methylisocyanide on reduction using Li AlH4 gives:

(a)

Methyl amine

(b)

Ethyl amine

(c)

Dimethyl amine

(d)

Trimethyl amine

15. At pH 12, glycine exists as

(a)

H3N+ - CH2 - COOH

(b)

H2N - CH2 - COO-

(c)

H3N+ - CH2-COO-

(d)

H2N - CH2 - COOH

16. Part II

Answer any 6 questions. Question no. 24 is compulsory.

9 x 2 = 18
17. What is meant by concentration?

18. Give the uses of Borax

19. Account for the following:
(i) O-O bond lengths in ozone molecule are identical.
(ii) Most of the reactions in fluorine are exothermic.

20. Write the IUPAC name of [Ag(NH3)2]Cl.

21. Give any three characteristics of ionic crystals.

22. Mention the factors that affected the rate of a chemical reaction.

23. Indentify the conjugate acid base pair for the following reaction in aqueous solution
i) HS- (aq) + HF $\rightleftharpoons$ F-(aq) + H2S(aq)
ii) HPO2-+ SO32- $\rightleftharpoons$ PO43-+HSO3-
iii) NH4+ CO32-  $\rightleftharpoons$ NH3+HCO3-

24. Explain the function of a salt bridge in an electrochemical cell.

25. Arrange the following in the increasing order of their boiling point and give a reason for your ordering
(i) Butan – 2- ol, Butan -1-ol, 2 –methylpropan -2-ol
(ii) Propan -1-ol, propan -1,2,3-triol, propan -1,3 – diol, propan -2-ol

26. Part III

Answer any 6 questions. Question no. 33 is compulsory.

9 x 3 = 27
27. Write the chemical composition of the following alloys and give anyone of its application.
(i) Bronze
(ii) Brass
(iii) Stainless steelass

28. Complete the following reactions?
i) Cr2 + 2e-
ii) Mn2+ + 2e- ⟶
iii) Fe2+ + 2e
iv) CO2+ + 2e-

29. Corrosion of aluminum takes place at a much slower rate than iron. Give reason

30. Peptising agent is added to convert precipitate into colloidal solution. Explain with an example.

31. Account for the following: (i) Phenol has a smaller dipole moment than methanol, (ii) Phenols do not give protonation reaction readily.

32. An alkene (A) on ozonolysis gives propanone and aldehyde (B). When (B) is oxidised (C) is obtained. (C) is treated with BriP gives (D) which on hydrolysis gives (E). When propanone is treated with HCN followed by hydrolysis gives (E). Identify A) B) C) D and E.

33. How will convert nitrobenzene to benzoic acid?

34. Write a reaction that indicates the presence of an aldehyde group in glucose.

35. Give the structure of melamine formaldehyde resin.

36. Part IV

10 x 5 = 50
37. Write a note on zeolites.

38. How is chlorine manufactured by the electrolysis of brine.

39. Justify the following statement.
"Elements of the first transition series possess many properties different from those of heavier transition elements".

40. What is meant by stability of a co-ordination compound in solution? State the factors which govern stability of complexes.

41. How are crystals classified?

42. A zero order reaction is 20% complete in 20 minutes. Calculate the value of the rate constant. In what time will the reaction be 80% complete?

43. Write the expression for the solubility product of Hg2Cl2 .

44. Give the special characteristics of enzyme catalysed reactions.

45. Identify A,B,C,D and write the compelete equation

46. An organic compound (A) of molecular formula C7Hon oxidation with air and in presence of V2O5 to form (B) of molecular formula C7H6O. (B) on reduction with lithium aluminium hydride to form (C) of . molecular formula C7H5O. Identify (A)(B) and (C) and explain th.e reactions.