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

12th Standard EM

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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. Which of the following is commonly used to produce foam in froth floatation process?

(a)

Pine oil

(b)

Cresol

(c)

NaCN

(d)

Xanthate

2. The repeating unit in silicone is v

(a)

SiO2

(b)

(c)

(d)

3. The ionisation energy of Ga is higher than that of Al because of_________

(a)

more effective nuclear charge of Ga

(b)

smaller atomic size of Ga

(c)

larger size ofGa

(d)

both (a) and (b)

4. Which one of the following is not correct?

(a)

La(OH)2 is less basic than Lu(OH)3

(b)

In lanthanoid series ionic radius of Ln3+ ions decreases

(c)

La is actually an element of transition metal series rather than lanthanide series

(d)

Atomic radii of Zr and Hf are same because of lanthanide contract

5. An excess of silver nitrate is added to 100ml of a 0.01M solution of pentaaquachloridochromium(III)chloride. The number of moles of AgCl precipitated would be

(a)

0.02

(b)

0.002

(c)

0.01

(d)

0.2

6. 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

7. What is the activation energy for a reaction if its rate doubles when the temperature is raised from 200K to 400K? (R = 8.314 JK-1mol-1)

(a)

234.65 kJ mol-1 K-1

(b)

434.65 kJ mol-1 K-1

(c)

434.65 J mol-1 K-1

(d)

334.65 J mol-1 K-1

8. Conjugate base for bronsted acids H2O and HF are

(a)

OH- and H2FH+ , respectively

(b)

H3O+ and F, respectively

(c)

OH- and F-, respectively

(d)

H3O+ and H2F+, respectively

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. An example of secondary cell is ____________

(a)

Daniel cell

(b)

galvanic cell

(c)

(d)

dynam

11. In an electrical field, the particles of a colloidal system move towards cathode. The coagulation of the same sol is studied using K2SO4 (i), Na3 PO4 (ii),K4 [Fe(CN)6] (iii) and NaCl (iv) Their coagulating power should be

(a)

II > I>IV > III

(b)

III > II > I > IV

(c)

I> II > III > IV

(d)

none of these

12. The test used to distinguish wish 10, 20 and 30 alcohol is ________

(a)

Lucas test

(b)

Victor Meyer's

(c)

dehydrogenation

(d)

all the above

13. Which one of the following reaction is an example of disproporationation reaction

(a)

Aldol condensation

(b)

cannizaro reaction

(c)

Benzoin condensation

(d)

none of these

14. Amine that cannot be prepared by Gabriel Phthalimide synthesis is ___________

(a)

benzyl amine

(b)

methyl amine

(c)

ethyl amine

(d)

phenyl amine

15. Insulin is an example of_______hormone.

(a)

paracrine

(b)

endocrine

(c)

autocrine

(d)

none of the above

16. Part II

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

6 x 2 = 12
17. Discuss the use of an acidic flux in metallurgy.

18. Boron does not react directly with hydrogen. Suggest one method to prepare diborane from BF3.

19. How would you account for the following? The electron gain enthalpy with negative sign is less for oxygen than that of sulphur.

20. What are stereoisomers?

21. Give any three characteristics of ionic crystals.

22. H2(g) + Cl2(g) $\overset { hv }{ \longrightarrow }$ 2HCl(g). The reaction proceeds with a uniform rate throughout. What do you conclude?

23. When aqueous ammonia is added to CuSO4 solution, the solution turns deep blue due to the formation of tetramminecopper (II) complex, ${ [Cu({ H }_{ 2 }O)] }_{ (aq) }^{ 2+ }\rightleftharpoons 4{ NH }_{ 3 }(aq)\rightleftharpoons { [Cu{ ({ NH }_{ 3 }) }_{ 4 }] }_{ (aq) }^{ 2+ }$ among H2O and NH3 Which is stronger Lewis base.

24. What is the anode, cathode and electrolyte of a mercury button 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.

6 x 3 = 18
27. List the applications of gold

28. Give reason for the following:
(i) A transition metal exhibits highest oxidation state in oxides and fluorides.
(ii) Cu2+ is unstable in an aqueous solution.

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

30. What are the factors which influence the adsorption of a gas on a solid?

31. Halo alkane are easily prepared from alcohols while aryl halides cannot be prepared from phenol.- Justify.

32. How will you convert benzaldehyde into the following compounds?
(i) benzophenone
(ii) benzoic acid
(iii) hydroxyphenylaceticacid.

33. Write a note on structure of amine.

34. Name two water soluble vitamins, their sources, function and diseases caused due to their deficiency in diet.

35. Give the structure of melamine formaldehyde resin.

36. Part IV

5 x 5 = 25
1. 0.44g of a monohydric alcohol when added to methyl magnesium iodide in ether liberates at STP 112 cm3 of methane with PCC the same alcohol form a carbonyl compound that answers silver mirror test. Identify the compound.

2. An aromatic aldehyde (A) of molecular formula C7H6O which has the smell of bitter almonds on treatment with (CH3CO)2O and CH3COONa to give compound (B) which is an aromatic unsaturated add. (A) also reacts with (A) in the presence of ale. KCN to give dimer (C). Identify (A), (B) and (C). Explain the reactions.

1. Calculate i) the hydrolysis constant, ii) degree of hydrolysis and iii) pH of 0.1M CH3COONa solution (pKa for CH3COOH is 4.74).

2. Name the method to deduce the charge of the sol particle. Explain it with a neat diagram.

1. How are crystals classified?

2. A first order reaction is 40% complete in 50 minutes. Calculate the value of the rate constant. In what time will the reaction be 80% complete?

1. How are materials classified based on their magnetic properties?

2. Give the IUPAC name for the following compounds.
(i) [Ag(NH3)2]CI
(ii) K3[Fe(CN)5NO]
(ill) [Cr(PPh3)(CO)3]
(iv) [Ag(NH3)2]+
(v) [FeF6]4-

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

2. Why is dioxygen a gas but sulphur a solid?