Kendriya Vidyalaya Ntpc Shaktinagar

KENDRIYA VIDYALAYA NTPC SHAKTINAGAR

PRE BOARD – 1 EXAMINATION (2015-16)

Subject - CHEMISTRY (Theory)

Class – XII

Time allowed: 3 hours Maximum Marks: 70

General Instructions:

a) All the questions are compulsory.

b) There are 26 questions in total.

c) Questions 1 to 5 are very short answer type questions and carry one mark each.

d) Questions 6 to 10 carry two marks each.

e) Questions 11 to 22 carry three marks each.

f) Question23 is value based question carrying four marks.

g) Questions 24 to 26 carry five marks each.

h) There is no overall choice. However, an internal choice has been provided in one question of

two marks, one question of three marks and all three questions in five marks each. You have

to attempt only one of the choices in such questions.

Use of calculators is not permitted. However, you may use log tables if necessary.

1. Why is ferric chloride preferred over potassium chloride to stop bleeding from cuts?

2.What do you understand by ‘colligative properties’?

3. Give the IUPAC name of the following compound CH3 – CH2 – CH2 – O – CH3.

4. Predict the shape of ClF3on the basis of VSEPR theory.

5. Give an account for the miscibility of ethoxyethane with water?

6.Define the term Coagulation and Peptisation.

7.A solution of glycerol (C3H8O3) was prepared by dissolving some glycerol in 500 g of water. The solution has a boiling point 100.42 oc.What mass of glycerol was dissolved to make this solution? (k b for water = 0.512 kg mol -1 ).

8. (a) What is the covalence of nitrogen in N2O5?

b) Explain why both N and Bi do not form pentahalides while phosphorus does.

When conc. H2SO4 was added into an unknown salt present in atest tube, a brown gas A

was evolved. This gas intensified when copper turnings were also added into this test

tube. On cooling the gasA changed intoa colorless gas B.

(i). Identify the gas A and B

(ii). Write the equation for the reaction involved.

9. Arrange the following in decreasing order of basic strength in the gas phase and justify your

answer.

C2H5NH2 , (C2H5)2NH2 , (C2H5)3N, NH3

10. Write the formula of major product formed in the following chemical reactions:

(a) CH3Br + alc. AgCN ------

(B)C2H5NH2 + CHCl3 + KOH(alc) ------

11.Define the term osmotic pressure, how the molecular mass of a substance can be determined by a method based on measurement of osmotic pressure?.

12. Write names of monomers of the following polymers and classify them as addition or

Condensation polymers.

(a) Teflon

(b) Nylon-6,6

13. (a) Give the electronic configuration of the d-orbitals of Ti in [Ti(H2O)6]3+ion in an octahedral

crystal field.

b) Explain why this complex is coloured based on the distribution of electrons in the dorbitals.

c) How does the colour change on heating [Ti(H2O)6]3+ion?

14.Define order of reaction. A reaction is of second oeder with respect to a reactant. How is the rate of reaction affected if the concentration of the reactant is reduced to half? What is the unit of rate constant for such a reaction?

15. What are the two classes of emulsions? Give one example of each. Explain two activities to

Identify the type of a given emulsion.

Describe the following features of surface catalysts by giving an example.

a) Activity

b) Selectivity

16. Explain:

(i) The presence of a base is needed in the ammonolysis of alkyl halides.

(ii) Aromatic primary amines cannot be prepared by Gabriel Phthaliminde synthesis.

(iii) Write the IUPAC name of: CH3 – N (C2H5) – CO – CH3

17. Explain the following facts :-

(a) Transition metals act as catalysts.

(b) Chromium group elements have the highest melting points in their respective series.

18. (a) Give the IUPAC name of [Cr Cl2 (H2O)4]Cl.

b) Give the number of unpaired electrons in the following complex ions [FeF6]4-and [Fe (CN)6]4-

c) Name the isomerism exhibited by the following pair of coordination compounds

|Co(NH3)5Br| SO4 and |Co(NH3)5SO4|Br

19. Define the tern activation energy. A first order reaction takes 40 minute for 30% decomposition. Calculate t1/2.

20. How are vitamins classified? Name the vitamin responsible for coagulation of blood.

Why are vitamin A and vitamin C essential to us? Give their important sources.

What happens when GLUCOSE is treated with (i) Br2 water (ii) Conc.HNO3 (iii) HI

21. Name the most symmetrical and (ii) most unsymmetrical cubic structures.

Analysis shows that nickel oxide has the formula Ni0.98O1.00. What fractions of the nickel exist as Ni2+ and Ni3+?

22. (a) Give one chemical test to distinguish between the following pairs.

(i) Ethyl amine and diethyl aminel

(ii) Alcohol and phenoll.

(iii) Benzaldehyde and acetophenone

How will you convert the following–

(i) Benzene to Toluene

(ii) Aniline to Chloro benzene

(iii) Ethanol to Ethanoic acid

23.Shyam Prasad is a farmer and has 33 acre of land on which he has grown crops.One day two of his friends come to visit him.He takes them to show crops proudly.One of his friend notices some infection on the leaves of hos crops.Headvises him to use DDT.The other friend instead advises him to use dry power of neem leaves as insecticide.

(i) Whose advise should Shyam Prasad take and why?

(ii) What effect can DDT poses?

(iii) Write values associated with above decision?

24. Give reasons for the following:-

a) PH3 has lower boiling point than NH3

b) Yellow P4 is less stable and more reactive than other allotropes.

c) AgCl is sparingly soluble in water but dissolves completely in NH4OH.

d) Nitrogen (II) Oxide undergoes dimerization.

e) PCl3 fumes in moist air.

Answer the following :-

a) Why is ozone a powerful oxidizing agent?

b) Why ICl is more reactive than I2?

c) Name two poisonous gases that can be prepared using chlorine gas.

d) Why is fluorine a stronger oxidizing agent than chlorine?

e) Give two uses of Neon.

25. (a) Define molar conductivity and specific conductivity and give the relationship between them.

(b).Calculate the emf of the following cell at 298 K :

Mg(s) /Mg 2+(0.001M // Cu 2+(0.0001 M / Cu(s)

Given: - Mg 2+/Mg = -2.37V, Cu2+/Cu = +0.34V

26. Write the equations of the following reactions:-

(i) Cannizaros reaction

(ii) Hofman bromide reaction

(iii) HVZ reaction

(iv) Clemenson reduction

(v) Aldol condensation

(A).How will you convert the following-

(i).Propene to 1-Propanol

(ii).Phenol and Salicylic acid.

(B).How will you distinguish between –

(i). Ethanal and propanone.

(ii).Phenol and ethanoic acid.

(iii).Prmary amine and secondary amine.