#### 12th Standard Chemistry English Medium Reduced Syllabus Model Question paper - 2021 Part - 1

12th Standard

Reg.No. :
•
•
•
•
•
•

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. Zinc is obtained from ZnO by

(a)

Carbon reduction

(b)

Reduction using silver

(c)

Electrochemical process

(d)

Acid leaching

2. Which of the following is not true with respect to Ellingham diagram?

(a)

Free energy changes follow a straight line. Deviation occurs when there is a phase change.

(b)

The graph for the formation of CO2 is a straight line almost parallel to free energy axis.

(c)

Negative slope of CO shows that it becomes more stable with increase in temperature

(d)

Positive slope of metal oxides shows that their stabilities decrease with increase in temperature

3. Oxidation state of carbon in its hydrides

(a)

+4

(b)

-4

(c)

+3

(d)

+2

4. Which of the following is strongest acid among all?

(a)

HI

(b)

HF

(c)

HBr

(d)

HCl

5. Which one of the following statements related to lanthanons is incorrect?

(a)

Europium shows +2 oxidation state

(b)

The basicity decreases as the ionic radius decreases from Pr to Lu.

(c)

All the lanthanons are much more reactive than aluminium

(d)

Ce4+ solutions are widely used as oxidising agents in volumetric analysis.

6. 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

7. 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)

8. An ionic compound AxBy 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 AxBy is

(a)

AB

(b)

AB3

(c)

A3B

(d)

A8B6

9. The number of carbon atoms per unit cell of diamond is

(a)

8

(b)

6

(c)

1

(d)

4

10. The fraction of total volume occupied by the atoms in a simple cubic is

(a)

$\left( \cfrac { \pi }{ 4\sqrt { 2 } } \right)$

(b)

$\left( \cfrac { \pi }{ 6 } \right)$

(c)

$\left( \cfrac { \pi }{ 4 } \right)$

(d)

$\left( \cfrac { \pi }{ 3\sqrt { 2 } } \right)$

11. Among the following graphs showing variation of rate constant with temperature (T) for a reaction, the one that exhibits Arrhenius behavior over the entire temperature range is

(a)

(b)

(c)

(d)

both (b) and (c)

12. Predict the rate law of the following reaction based on the data given below
$2A+B\longrightarrow C+3D$

 Reaction number [A] (min) [B] (min) Initial rate (M s-1) 1 0.1 0.1 x 2 0.2 0.1 2x 3 0.1 0.2 4x 4 0.2 0.2 8x
(a)

rate=k[A]2[B]

(b)

rate=k[A][B]2

(c)

rate=k[A][B]

(d)

rate=k[A]1/2[B]1/2

13. This reaction follows first order kinetics. The rate constant at particular temperature is 2.303X10-2 hour-1 The initial concentration of cyclopropane is 0.25 M. What will be the concentration of cyclopropane after 1806 minutes? (log 2 = 0.3010)

(a)

0.125 M

(b)

0.215 M

(c)

0.25 x 2.303 M

(d)

0.05 M

14. Using Gibb’s free energy change, ∆Go=57.34 kJ mol-1, for the reaction, X2Y(s)⇌2X++Y2- (aq), calculate the solubility product of X2Y in water at 300 K (R = 8.3 J K-1Mol-1)

(a)

10-10

(b)

10-12

(c)

10-14

(d)

can not be calculated from the given dat

15. The button cell used is watches function as follows
Zn (s) + Ag2O (s) + H2O (l) ⇌ 2Ag (s) + Zn2+ (aq) + 2OH-(aq)the half cell potentials
are Ag2 O (s) + H2O (l) + 2e- →2Ag (s) + 2OH- (aq) Eo.34V The cell potential will be

(a)

0.84V

(b)

1.34V

(c)

1.10V

(d)

0.42V

1. Part II

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

9 x 2 = 18
16. Define Deemulsification.

17. Name the types of emulsions.

18. Why sodium metal cannot be used to dry alcohols but it can be used to dry ethers?

19. How will you distinguish between formaldehyde and acetaldehyde?

20. Give the structural formula of
i) 2-amino-2-methyl propane
ii) 2-(N, N- dimethyl) amino butane

21. ${ C }_{ 6 }{ H }_{ 5 }{ NH }_{ 2 }\xrightarrow [ 273k,HCl ]{ { HNO }_{ 2 } } A\xrightarrow [ { Cu }_{ 2 }({ CN })_{ 2 } ]{ KCN } B\underrightarrow { { H }_{ 3 }O } C$
Identify A, Band C.

22. Use the following reagents in the correct order and bring about the conversion of benzene to aniline.
Reagents - HCI, NH3, heat, alk KMnO4, CHCl/ AlCl3, Br2/KOH that can be used.

23. Give the IUPAC name of the following compounds
i) ${ H }_{ 3 }C-\underset { \overset { | }{ CN } }{ CH } -{ CH }_{ 2 }-COOH$
ii) ${ CH }_{ 3 }-\underset { \overset { | }{ { CH }_{ 3 } } }{ CH } -CN$
iii) C6H5-NC

24. Name the vitamin responsible for coagulation of blood.

1. Part III

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

9 x 3 = 27
25. Give examples for first order reaction.

26. Explain the relationship between free energy of the cell and its emf.

27. Write a note on Ultrafilteration?

28. Complete the following equations by writing the missing A, B, C, D etc.,

29. Write short notes on Popoff's rule.

30. How are the following compounds obtained from benzene diazonium chloride?
(i) phenol
(ii) ester
(iii) p-hydroxy azo benzene

31. ExpIain the classification of proteins based on their structure.

32. Write a note on tertiary structure of proteins.

33. Give the structure of sucrose.

1. Part IV

10 x 5 = 50
34. Explain the principle of electrolytic refining with an example.

35. How will you identify borate radical?

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

37. The E0M2+/M value for copper is positive. Suggest a possible reason for this.

38. Why first ionization enthalpy of chromium is lower than that of zinc?

39. Aluminium crystallizes in a cubic close packed structure. Its metallic radius is 125pm. calculate the edge length of unit cell.

40. 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?

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

42. 8.2$\times$1012 litres of water is available in a lake. A power reactor using the electrolysis of water in the lake produces electricity at the rate of    2$\times$106 Cs−1 at an appropriate voltage. How many years would it like to completely electrolyse the water in the lake. Assume that there is no loss of water except due to electrolysis.

43. Complete the following reactions
i) CH3- CH2 - OH $\overset { { P}{ Br_3 }{ } }{ \underset { {} }{ \longrightarrow } }$  A  $\overset { { aq.NaOH}{ }{ } }{ \underset { {} }{ \longrightarrow } }$ B $\overset { { Na}{ } }{ \underset { {} }{ \longrightarrow } }$
ii) C6H5- OH  $\overset { { Zndert}{ } }{ \underset { {} }{ \longrightarrow } }$ A $\overset { { CH_3}{Cl}{ } }{ \underset { {Anhydrs}{AlCl_3} }{ \longrightarrow } }$ B $\overset { { acid}{K MnO_4}{ } }{ \underset { {} }{ \longrightarrow } }$ C