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#### Public Model Question Paper Part-VI 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. The blistered appearance of Cu obtained from the reverberatory furance is due to evolution of

(a)

CO2 gas

(b)

S02 gas

(c)

NO2

(d)

Due to evaporation of volatile materials

2. 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

3. Orthophosphorus acid on heating gives________

(a)

Hypophosphorus

(b)

Orthophosphoric acid

(c)

Phosphine gas

(d)

both (b) and (c)

4. The magnetic moment of Mn2+ ion is

(a)

5.92BM

(b)

2.80BM

(c)

8.95BM

(d)

3.90BM

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. For a solid with the following structure. The co-ordination number of the point B is__________

(a)

3

(b)

4

(c)

5

(d)

6

7. After 2 hours, a radioactive substance becomes $\left( \cfrac { 1 }{ 16 } \right) ^{ th }$ of original amount Then the half life ( in min) is

(a)

60 minutes

(b)

120 minutes

(c)

30 minutes

(d)

15 minutes

8. pH of a saturated solution of Ca(OH)2 is 9. The Solubility product ( Ksp) of Ca(OH)2

(a)

0.5 ×10-15

(b)

0.25 ×10-10

(c)

0.125 ×10-15

(d)

0.5 ×10-10

9. Degree of dissociation a is

(a)

$\alpha =\frac { { K }_{ a } }{ C }$

(b)

$\alpha =\frac { { C }^{ 2 } }{ { K }_{ a } }$

(c)

$\alpha =\sqrt { \frac { { K }_{ a } }{ C } }$

(d)

$\alpha =\sqrt { \frac { C }{ { K }_{ a } } }$

10. Degree of dissociation of pure water is 2.8 x 10-9. Molar ionic conductance of H+ and OH- ions at infinite dilution are 300 and 350 S cm2 respectively. The molar conductance of water is ________

(a)

1.5 x 10-6 S mol-1

(b)

2.8 x 10-7 S cm2 mol-1

(c)

1.82 x 10-6 S cm2 mol-1

(d)

3.8 x 10-6 S cm-1 mol-1

11. The phenomenon observed when a beam of light is passed through a colloidal solution is

(a)

Cataphoresis

(b)

Electrophoresis

(c)

Coagulation

(d)

Tyndall effect

12. The number of primary alcoholic groups in ethylene glycol is _________

(a)

0

(b)

1

(c)

2

(d)

3

13. (a)

(b)

(c)

(d)

14. C6H5CHO + Methylamine ⟶ X Y + H2SO4-p pamino benzene sulphonic acid.
Then X and Y are

(a)

Schiff's Base, C6H5NH2

(b)

C6H6, C6H5CHO

(c)

benzal- N - methyl amine, Toluene

(d)

None of these

15. Glucose forms________with acetic anhydride and sodium acetate.

(a)

di acetate

(b)

tetra acetate

(c)

penta acetate

(d)

hexa acetate

16. Part II

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

6 x 2 = 12
17. What is distillation?

18. Give the structure of CO and CO2.

19. Elements of group 16 show lower value of first ionization enthalpy compared to group 15, why?

20. What is Co-ordination sphere?

21. Give any three characteristics of ionic crystals.

22. For a chemical reaction, Variation in the concentration In[A] Vs time in seconds is given as

(i) What is the order of the reaction?
(ii) What is the unit of rate constant K?
(iii) Give the relationship between k and ${ t }_{ \frac { 1 }{ 2 } }$

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. Account for the following : For a strong electrolyte molar conductivity decreases as concentration increases

25. Draw the major product formed when 1-ethoxyprop-1-ene is heated with one equivalent of HI

26. Part III

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

6 x 3 = 18
27. What is cyanide leaching? Give an example

28. What is chromyl chloride test? Give equations.

29. What is the oxidation and reduction half cell in a Daniel cell?

30. Why are lyophillic colloidal sols are more stable than lyophobilc colloidal sol.

31. How is glycerol obtained commercially? State its uses.

32. What is the action of HCN on
(i) propanone
(ii) 2,4-dichlorobenzaldehyde.

33. Starting from the following reagents, how will your prepare ethanenitrile.
i) CH3Br
ii) CH3CONH2
iii) CH3CH=NOH

34. Justify the presence of keto group in C2 in fructose.

35. Write the preparation of neoprene and give its use.

36. Part IV

5 x 5 = 25
1. Phenol is distilled with Zn dust followed by friedel – crafts alkylation with prophyl chloride to give a compound B, B on oxidation gives (c) Indentify A,B and C.

2. An organic compound (A) of molecular formula C7H6O is called as oil of bitter almonds. (A) on oxidation gives (B) of molecular formula C7H6O2 which gives brisk effervescence with NaHCO3 solution. When (A) is refluxed with aqueous alcoholic (KCN) compound (C) is formed. Identify A) Band C and write the equations.

1. Ksp of AgCl is $1.8\times10^{-10}$. Calculate molar solubility in 1 M AgNO3

2. Write the characteristics of catalysts.

1. What are stoichiometric defects in ionic solids? Explain

2. The time for half change in a first order decomposition of a substance A is 60 seconds. Calculate the rate constant. How much of A will be left after 180 seconds?

1. Complete the following reactions
(i) Cr2O72-
(ii) Cr2O7- + 6I-+ 14H+ ⟶
(iii)  Cr2O7- + 3S2-+ 14H+ ⟶
(iv) Cr2O7- + 3SO2+ 14H+
(v) Cr2O7- +3Sn2+ + 14H+ ⟶
(vi) K2Cr2O7 + 8H2SO4 + 3CH3CH2OH ⟶
(vii) 2MnO4- + 5(COO)2- + 6H+ ⟶
(viii) 2MnO4- + 10I+ 16H+
(ix) 2MnO4- + 5S2-+ 16H+ ⟶
(x) 2MnO4- + 5NO2- + 6H+ ⟶
(xi) 2KMnO4 + 3H2SO4 + 5CH3CH2OH ⟶
(xii) 2MnO4- + 5SO32- + 6H+

2. How are Co-ordination compounds classified?

1. Write a note on zeolites.

2. How is sulphuric acid manufacture by contact process?