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QUARTERLY EXAM - 2019

12th Standard EM

Reg.No. :
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Chemistry

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

PART - I

15 x 1 = 15
1. Match items in column - I with the items of column – II and assign the correct code.

 Column-I Column-II A. Cyanide process (i) Ultrapure Ge B Froth floatation process (ii) Dressing of ZnS C Electrolytic reduction (iii) Extraction of Al D Zone refining (iv) Extraction of Au (v) Purification of Ni
(a)
 A B C D
(b)
 A B C D (i) (ii) (iii) (iv)
(c)
 A B C D (iii) (iv) (v) (i)
(d)
 A B C D (ii) (iii) (i) (v)
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. Which of the following is not sp2 hybridised?

(a)

Graphite

(b)

graphene

(c)

Fullerene

(d)

dry ice

4. Which one of the following compounds has similar structure to that of graphite?

(a)

Boron nitride

(b)

Boron Carbide

(c)

Aluminium Carbide

(d)

Aluminium Oxide

5. Solid (A) reacts with strong aqueous NaOH liberating a foul smelling gas(B) which spontaneously burn in air giving smoky rings. A and B are respectively

(a)

P4(red) and PH3

(b)

P4(white) and PH3

(c)

S8 and H2S

(d)

P4(white) and H2S

6. Assertion : bond dissociation energy of fluorine is greater than chlorine gas
Reason: chlorine has more electronic repulsion than fluorine.

(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 catalytic behaviour of transition metals and their compounds is ascribed mainly due to

(a)

their magnetic behaviour

(b)

their unfilled d orbitals

(c)

their ability to adopt variable oxidation states

(d)

their chemical reactivity

8. 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.

9. The landthanide contraction is responsible for the fact that

(a)

Zr and Zn have the same oxidation state

(b)

Zr and Hf have almost the same radius

(c)

Zr and Nb have similar oxidation state

(d)

Zr and Y have similar radius

10. Which one of the following will give a pair of enantiomorphs?

(a)

[Cr(NH3)6][Co(CN)6]

(b)

[Co(en)2Cl2]cl

(c)

[pt(NH3)4][ptcl4]

(d)

[Co(NH3)4Cl2]NO2

11. Choose the correct statement

(a)

Square planar complexes are more stable than octahedral complexes

(b)

The spin only magnetic moment of [Cu(Cl)4]2- is BM and it has square planar structure.

(c)

Crystal field splitting energy $\left( { \Delta }_{ 0 } \right)$ [FeF6]4- is higher than the $(\Delta _{ 0 })$ $[Fe(CN)6]{ { 4 }^{ - } }$

(d)

crystal field stabilization energy of [V(H2O)6]2+ is higher than the crystal field stabilization of [Ti(H2O)6]2+

12. Primary valency corresponds to the ______________

(a)

oxidation state of the metal

(b)

co-ordination number

(c)

number of ligands

(d)

charge on the complex

13. CsCl has bcc arrangement, its unit cell edge length is 400pm, its inter atomic distance is

(a)

400pm

(b)

800pm

(c)

$\sqrt { 3 } \times 100pm$

(d)

$\left( \cfrac { \sqrt { 3 } }{ 2 } \right) \times 400pm$

14. Consider the following statements :
(i) increase in concentration of the reactant increases the rate of a zero order reaction.
(ii) rate constant k is equal to collision frequency A if Ea = 0
(iii) rate constant k is equal to collision frequency A if Ea =0
(iv) a plot of ln (k) vs T is a straight line.
(v) a plot of ln (k) vs $\left( \cfrac { 1 }{ T } \right)$ is a straight line with a positive slope.
Correct statements are

(a)

(ii) only

(b)

(ii) and (iv)

(c)

(ii) and (v)

(d)

(i), (ii) and (v)

15. Which of the following statement is not correct?

(a)

Molecularity of a reaction cannot be fractional

(b)

Molecularity of a reaction cannot be more than three

(c)

Molecularity of a reaction can be zero

(d)

Molecularity is assigned for each elementary step of mechanism.

16. PART - II WRITE ANY 7  QUESTIONS. Q.NO  24 IS COMPULSORY

6 x 2 = 12
17. Which type of ores can be concentrated by froth floatation method? Give two examples for such ores.

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

19. Name the building block of zeolites. Why zeolites have high porosity?

20. Chalcogens belongs to p-block. Give reason.

21. Justify the position of lanthanides and actinides in the periodic table.

22. Draw all possible geometrical isomers of the complex [Co(en)2]+ and identify the optically active isomer.

23. Differentiate crystalline solids and amorphous solids.

24. Define half life of a reaction. Show that for a first order reaction half life is independent of initial concentration

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

26. PART - III  WRITE ANY 7  QUESTIONS. Q.NO  32 IS COMPULSORY

6 x 3 = 18
27. Explain the electrometallurgy of aluminium

28. Describe the structure of diborane

29. Find out the oxidation state of carbon in each of the following:
(i) CaC2
(ii) H2CO3
(iii) HCN
(iv) CO

30. Give a reason to support that sulphuric acid is a dehydrating agent.

31. Compare lanthanides and actinides

32. Write briefly about the applications of coordination compounds in volumetric analysis

33. Calculate the percentage efficiency of packing in case of body centered cubic crystal.

34. Silver crystallines in fcc lattice. If edge length of the cell is 4.07 x 10-8 em and density is 10.5 g cm-3. Calculate the atomic mass of silver

35. Explain briefly the collision theory of bimolecular reactions

36. PART - IV WRITE ANY  5  QUESTIONS

5 x 5 = 25
1. Describe the role of the following in the process mentioned.
(i) Silica in the extraction of copper.
(ii) Cryolite in the extraction of aluminium.
(iii) Iodine in the refining of Zirconium.
(iv) Sodium cyanide in froth floatation.

2. Explain the principle of electrolytic refining with an example.

1. Give a reaction between nitric acid and a basic oxide.

2. Why do zirconium and Hafnium exhibit similar properties?

1. Discuss briefly the nature of bonding in metal carbonyls

2. What are the limitations of VB theory?

1. 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 will you convert boric acid to boron nitride?

2. Deduce the oxidation number of oxygen in hypofluorous acid – HOF.

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

2. How do nature of the reactant influence rate of reaction.