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) Ă 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 Ă 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 ![clip_image007[1]](http://www.education2home.com/wp-content/uploads/2012/03/clip_image0071_thumb.gif "clip_image007[1]")
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 kp and kc 3
b) The value of kc 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 Ă
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
![clip_image007[1]](http://www.education2home.com/wp-content/uploads/2012/03/clip_image0071.gif "clip_image007[1]"){kind=small}
