Half Yearly Model Question Paper 2019

12th Standard EM

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Chemistry

Time : 02:30:00 Hrs
Total Marks : 70

Part A

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

15 x 1 = 15
1. The incorrect statement among the following is

(a)

Nickel is refined by Mond’s process

(b)

Titanium is refined by Van Arkel’s process

(c)

Zinc blende is concentrated by froth floatation

(d)

In the metallurgy of gold, the metal is leached with dilute sodium chloride solution

2. AlF3 is soluble in HF only in the presence of KF. It is due to the formation of (NEET)

(a)

K3[AIF3H3]

(b)

K3[AiF6]

(c)

AIH3

(d)

K[AIF3H]

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. Among the transition metals of 3d series, the one that has highest negative $\left( \frac { M^{ 2+ } }{ M } \right)$ standard electrode potential is

(a)

Ti

(b)

Cu

(c)

Mn

(d)

Zn

5. Which of these statements about [Co(CN)6]3- is true?

(a)

[CO(CN)6]3- has four unpaired electrons and will be in a high spin configuration

(b)

[Co(CN)6]3- has four unpaired electrons and will be in a low spin configuration

(c)

[CO(CN)6]3- has no unpaired electrons and will be in a high spin configuration

(d)

[CO(CN)6]3- has no unpaired electrons and will be in low spin configuration

6. Assertion : monoclinic sulphur is an example of monoclinic crystal system
Reason: for a monoclinic system, $a\neq b\neq c$ and $\alpha =\gamma ={ 90 }^{ 0 },\beta \neq { 90 }^{ 0 }$

(a)

Both assertion and reason are true and reason is the correct explanation of assertion

(b)

Both assertion and reason are true but reason is not the correct explanation of assertion.

(c)

Assertion is true but reason is false.

(d)

Both assertion and reason are false.

7. The Unit of rate constant and rate of reaction are same for

(a)

First order

(b)

second order

(c)

Third order

(d)

zero order

8. What is the pH of the resulting solution when equal volumes of 0.1M NaOH and 0.01M HCl are mixed?

(a)

2.0

(b)

3

(c)

7.0

(d)

12.65

9. 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

10. The most effective electrolyte for the coagulation of AS2S3Sol is

(a)

NaCl

(b)

Ba(NO3)2

(c)

K3[Fe(CN)6]

(d)

Al3+

11. Which of the following compounds on reaction with methyl magnesium bromide will give tertiary alcohol.

(a)

benzaldehyde

(b)

propanoic acid

(c)

methyl propanoate

(d)

acetaldehyde

12. 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

13. Which one of the following is most basic?

(a)

2,4 – dichloroaniline

(b)

2,4 – dimethyl aniline

(c)

2,4 – dinitroaniline

(d)

2,4 – dibromoaniline

14. In a protein, various amino acids liked together by

(a)

Peptide bond

(b)

Dative bond

(c)

$\alpha$-Glycosidic bond

(d)

$\beta$ - Glycosidic bond

15. Which is the monomer of neoprene in the following?

(a)

${ CH }_{ 2 }-\underset { \underset { CL }{ | } }{ C } { -CH=CH }_{ 2 }$

(b)

${ CH }_{ 2 }=CH-C\equiv CH$

(c)

${ CH }_{ 2 }=CH-CH={ CH }_{ 2 }$

(d)

${ CH }_{ 2 }-\underset { \underset { { CH }_{ 3 } }{ | } }{ C } { -CH=CH }_{ 2 }$

16. Part B

Answer any SIX questions. Question number 24 is compulsory

6 x 2 = 12
17. What is leaching?

18. What is the hybridisation of iodine in IF7? Give its structure?

19. Explain why compounds of Cu2+ are coloured but those of Zn2+ are colourless.

20. Arrange the following in order of increasing molar conductivity
(i) Mg[Cr(NH3)(Cl)5]
(ii) Cr(NH3)5Cl]3[CoF6]2
(iii) [Cr(NH3)3Cl3]

21. Define 'Ligand' Give an example of nautral legand.

22. Explain briefly seven types of unit cell

23. Account for the acidic nature of HClO4. In terms of Bronsted – Lowry theory, identify its conjugate base.

24. Identify the product (s) is / are formed when 1 – methoxy propane is heated with excess HI. Name the mechanism involved in the reaction

25. What are food preservatives?

26. Part C

Answer any SIX questions. Question number 33 is compulsory

6 x 3 = 18
27. How is acid leaching done for the sulphide ores?

28. Describe the structure of diamond.

29. How will you prepare chlorine in the laboratory?

30. What are redox reactions?

31. Give an example for complex of the type [Ma2b2c2] where a, b, c are monodentate ligands and give the possible isomers.

32. Why ionic crystals are hard and brittle?

33. How are the following conversions effected
i) benzylchloride to benzylalcohol
ii) benzyalalcohol to benzoic acid

34. Account for the following
i. Aniline does not undergo Friedel – Crafts reaction
ii. Diazonium salts of aromatic amines are more stable than those of aliphatic amines
iii. pKb of aniline is more than that of methylamine
iv. Gabriel phthalimide synthesis is preferred for synthesising primary amines.
v. Ethylamine is soluble in water whereas aniline is not
vi. Amines are more basic than amides
vii. Although amino group is o – and p – directing in aromatic electrophilic substitution reactions, aniline on nitration gives a substantial amount of m – nitroaniline.

35. Give two difference between Hormones and vitamins

36. Part D

5 x 5 = 25
1. 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.

2. Give three uses of emulsions.

1. Mention the type of hybridisation and magnetic property of the following complexes using VB theory a) [FeF6]4- b) [Fe(CN)6]4-

2. Ksp of Ag2 CrO4 is $1.1\times10^{-12}$.what is solubility of Ag2 CrO4 in 0.1M K2 CrO4.

1. Distinguish between diamond and graphite.

2. Mention the uses of helium

1. What is meant by the term “coordination number”? What is the coordination number of atoms in a bcc structure?

2. Write an account of the Arrhenius equation for rates of chemical reactions. (or) Write an account of the Arrhenius equation for  the effect of temperature on the rates of chemical reactions.

1. Why europium (II) is more stable than Cerium (II)?

2. Explain optical isomerism in coordination compounds with an example.