Class XI CBSE Chemistry Model Paper

Chemistry

Class – XI

Time – 3 Hrs. Marks – 70

General Instructions :

i) All questions are compulsory.

ii) Q. s 1 to 8 carry 1 makes each. Answer them in one word or in about on sentence.

iii) Q. s 9 to 18 carry 2 marks each. Answer these in about 30 words each.

iv) Q. s 19 to 27 carry 3 marks each. Answer these in about 40 words each.

v) Q. s 28 to 30 are long answer questions carrying 5 marks each.

vi) Use long table if necessary, use of calculator is not permitted.

1. Write IUPAC name of the following compound : 1

2. Write down the formula of the monomer of silicone. 1

3. What would be the effect of increasing pressure on the equilibrium. 1

PCl₅ (g) = Pcl₃ (g) + Cl₂ (g) ?

4. What is the oxidation number of oxygen in Na₂O₂ ? 1

5. What would be the sign of S for the process 2H (g) à H₂ (g) ? 1

6. What is compressibility factor of a gas ? 1

7. Configuration of ion M⁺² is Is² 2s² 2p⁵ what is configuration of atom M? 1

8. How many oxygen atoms would be there in 1 mole of H₂SO₄ ?

9. a) What is the hybridization of each carbon in CH₃ – CH₂ ? 1

b) What is the function of AlCl₃ (anhyd) in Friedel Crafts reaction ? 1

10. How N and S are detected when present in an organic compound together ? (Reaction only) 2

OR

Which is the electrophillic centre in CH₃Br and why ?

11. Why lithium does not form a superoxide but potassium does ? 2

OR

Why BeSO₄ is water soluble but BaSO₄ is not ?

12. Balance the following redox feaction by ion 2

Electron method :

Cr₂ O₇^-2 + Fe⁺² à Fe⁺³ + Cr⁺³ in acidic medium.

13. a) What is the change in internal energy in a process in which 700J of heat is absorbed and 450J of work is done by the system ?

b) Define a spontaneous process in terms of Gibbs energy. 1

14. Show by MO concept which one out of O₂ and O₂+ would be more stable. 2

OR

Explain all the orbital overlaps in a molecule of ethene (C₂H₄) by drawing a sutitable diagram.

15. Calculate the mass of (NH₄)₂ S required to prepare 200 ml of O.1 molar aqueous solution.

(N = 14, H = 1, S = 32)

16. a) Write down the IUPAC name and symbol of the element with at no 119. 1

b) Why Cl has more negative electron gain enthalpy then F in group 17 ? 1

17. Arrange the species : F^-, O^-2, N^-3, Mg ^{+ 2}, Al ^{+ 3} and Na⁺ in the increasing order of ionic radii and give reason. 2

18. Deduce the structural formula of an alkene which on ozonolysls produces propanal and pentanone – 2. 2

19. a) What is Eutrophication ? 1

b) How can photochemical smog be controlled ? 1

c) Give an example of herbicide. 1

20. a) Why atomic radius of Ga is less then the of Al in group 13 ? 1

b) Why white fumes appear around a bottle of anhydrous AlCl₃ ? 1

c) Why Sn⁺² is a reducing agent but Pb⁺² is not ? 1

21. Determine the percentage of Nitrogen in an organic compound, 0.5g of which on kjeldalisation required 10ml of 1M. H₂SO₄ for complete neuteralisation of the ammonia produced. 3

OR

What is the percentage of sulphur in an organic compound 0.15g of which on subjecting to carius method of suphur estimation produced 0.5g of BaSO4

(Ba = 137, S = 32, O = 16) ? 3

22. a) Explain the structure of diborane by drawing a suitable diagram. 2

b) Why SiCl₄ gets hydrolysed but CCl₄ does not ? 1

23. a) Write a reaction by which BeCl₂ can be prepared. 1 b) Why solvay process can not be extended to manfacture K₂CO₃ ? 1

c) Why salts of Be can not be detected by flame test ? 1

24. a) Why hard water does not give lather with soap ? 1

b) Complete the reaction and balance it 1

Pbs + H₂O₂

c) How the presence of H^-ions be confirmed in Ionic hydrides 1

25. For a reaction , H and S are 30.56 KJmol^-1 and 66JK^-1 mol^-1 respectively calculate the temperature above which the reaction

would be spontaneous. 3

26. a) Why does the viscosity of a liquid decreases with increase in temp ? 1

B) What is the pressure exerted by 2 mole of a gas enclosed in a 100ml vessel at 27⁰C ? (Given R = 0.0821 lit atm mol^-1 K^-1) 2

27. a) Why bond angle is NH₃ is lower that in CH₄ even though the same hybridization is involved in both cases ? 2

b) Why H₂O is polar but CO₂ is non polar ? 1

28. a) Mention two limitations of Bohr’s Model of atom 2

b) Calculate the wavelength of an electron moving with a kinetic energy of

3x10^-25J (mass of electran = 9.8 x 10^-31Kg) 3

OR

a) Out at 3d and 4s sub shells which one would have lower

energy and why ? 2

b) What would be the frequency of radiation emitted when an electron moving within a hydrogen atom undergoes transition from fifth to second energy level? 3

29. a) Derive the relationship between k_p and k_c 3

b) The value of k_c for the reaction

2A = B +C is 2 x 10^-3. At a given time the composition of reaction mixture is [A] = [B] = [C] = 3 x 10^-4 M. In which directions will the reaction proceed? 2

OR

a) Derive the relationship between Ka and α of a weak c molor acid HX. 3

b) Calculate the pH of 0.01 M KOH assuming complete dissociation. 2

30. a) Why wurtz reaction is not considered to be a suitable method for preparing

alkanes with odd no. carbon atoms ?

b) Explain the eclipsed and staggered conformation of ethane by Newman’s projection formula. 1

c) Complete the reaction : 1

CH₃ – CH₂ – CH = CH₂ + HBr à

OR

a) Explain the term β – elimination with an example. 2

b) Draw the Geometrical isomers of but – 2 – ene and explain which one would be polar. 2

c) Complete the reaction :

OH

+ Zn