#### 12th Standard English Medium Chemistry Reduced Syllabus Annual Exam Model Question Paper - 2021

12th Standard

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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. Sodium. magnesium and aluminum can be obtained from their ore by

(a)

electro metallurgy

(b)

pyro metallurgy

(c)

hydro metallurgy

(d)

smelting

2. Oxidation state of carbon in its hydrides ___________

(a)

+4

(b)

-4

(c)

+3

(d)

+2

3. S-S bond is present in

(a)

H2S2O7.

(b)

H2SO5

(c)

H2S2O6

(d)

H2S2O6

4. The alloy of copper that contain Zinc is

(a)

Monel metal

(b)

Bronze

(c)

bell metal

(d)

brass

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. 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

7. For a reaction Rate = kacetone[]32 then unit of rate constant and rate of reaction respectively is

(a)

(mol L-1 S-1),(mol1/2L1/2S-1)

(b)

(mol-1/2L1/2s-1),(mol L-1s-1)

(c)

(mol1/2L1/2s-1),(molL-1s-1)

(d)

(molLs-1),(mol1/2L1/2s)

8. Which of the following fluro – compounds is most likely to behave as a Lewis base?

(a)

BF3

(b)

PF3

(c)

CF4

(d)

SiF4

9. With regard to the strength of acids and bases, Find the incorrect statement among the following.

(a)

Strong acid is one that completely dissociates in water

(b)

Ka is the dissociation constant

(c)

CH3COOH is a weak acid

(d)

Smaller the Ka value, greater is the acid strength

10. The feasibility of a redox reaction can be predicted with the help of

(a)

Electronegativity

(b)

Electrochemical series

(c)

Electron affinity

(d)

Equivalent conductance

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. Glycol $\overset { 773K }{ \longrightarrow }$ 'A'. Identify 'A'

(a)

(b)

$\overset { { CH }_{ 3 } }{ \underset { CHO }{ | } }$

(c)

(d)

13. Benzoic acid $\overset { i){ NH }_{ 3 } }{ \underset { ii)\Delta }{ \longrightarrow } } A\overset { NaOBr }{ \longrightarrow } B\overset { NaN{ O }_{ 2 }/HCl }{ \longrightarrow } C \ 'C' \ is$ ____________

(a)

anilinium chloride

(b)

O – nitro aniline

(c)

benzene diazonium chloride

(d)

m– nitro benzoic acid

14. Oxidation of aniline with acidified potassium dichromate give

(a)

p-benzo quinone

(b)

benzoic acid

(c)

benzaldehyde

(d)

benzyl alcohol

15. The sugar unit present in nucleic acid is___________

(a)

a hexose

(b)

tetrose

(c)

pentose

(d)

glucose

16. Part II

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

6 x 2 = 12
17. Name the two steps involved in the extraction of crude metal

18. What is catenation ? describe briefly the catenation property of carbon

19. Give the reason for bleaching action of Cl2.

20. Draw the Cis and trans isomer of MA2B2 type

21. Distinguish tetrahedral and octahedral voids.

22. If the rate of a reaction gets doubled as the temperature is increased from 27oC to 37oC. Find the activation energy of reaction?

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. Give the uses of mercury button cell.

25. Suggest a suitable reagent to prepare secondary alcohol with identical group using Grignard reagent.

26. Part III

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

6 x 3 = 18
27. What is liquation?

28. Account for the following:
(i) Cobalt (II) is stable in aqueous solution but in the presence of complexing reagents, it is easily oxidised.
(ii) The d1 configuration is very unstable in ions.

29. Explain the process of recharging of lead storage battery.

30. What is the difference between a sol and a gel?

31. How is nitroglycerine .prepared from glycerol?

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

33. Convert aniline to p-nitro aniline

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

35. Give the structure of melamine formaldehyde resin.

36. Part IV

5 x 5 = 25
1. How will you convert boric acid to boron nitride?

2. Account for the following:
(i) Reducing character decreases from SO2 to TeO2.
(ii) Xenon forms compounds with fluorine and oxygen only.

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. What are the general characteristics of solids?

1. Give the structure for the following compounds.
(i) pentaamminechlorocobalt (III) ion
(ii) Triamminetrinitrito- k N cobalt (III)
(ill) tetraammineaquabromidooobalt(III)nitrate
(iv) Dichloridobisethane-1 )2-diamine) cobalt (lIl) chloride
(v) Tetraamminecopper (lI)sulphate

2. Benzene diazonium chloride in aqueous solution decomposes according to the quation ${ C }_{ 6 }{ H }_{ 5 }{ N }_{ 2 }Cl\longrightarrow { C }_{ 6 }{ H }_{ 5 }Cl+{ N }_{ 2 }$ Starting with an initial concentration of 101 g L-1, the volume of N2 gas obtained at 50 °C at different intervals of time was found to be as under:

 t(min) 6 12 18 24 30 $\infty$ Vol.of N2 (ml) 19.3 32.6 41.3 46.5 50.4 58.3

Show that the above reaction follows the first order kinetics. What is the value of the rate constant?

1. Ksp of Al(OH)3 is 1$\times$10-15M. At what pH does 1.0×10-3M Al3+ precipitate on the addition of buffer of NH4Cl and NH4OH solution?

2. Explain the following
(i) Reactant selectivity
(ii) Transition state selectivity
(iii) Product selectivity

1. Complete the following reactions

ii) $C_6H_5-CHCH(OH)CH(CH_3)_2 \overset{ConH_2SO_4}\longrightarrow$

2. Compound A of molecular formula C3H6O does not reduce Tollens reagent and Fehling's solution. Compound A undergoes Clemmensen reduction to give compound B of molecular formula C3H5' Compound A in the presence of cone. H2SO4 condenses to give an aromatic compound C of molecular formula C9H12.Identify A, Band C. Explain the reactions.