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Download CBSE Guess Papers Accountancy Class XII(12th) 2006

• Accountancy XII 2008 (Collection of 7 papers)
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FIRST TERM EXAMINATION

CLASS XII

CHEMISTRY THEORY

SET B

TIME ALLOWED: 3 HRS. MAXIMUM MARKS: 70

GENERAL INSTRUCTIONS

i. All questions are comuplsory

i. Marks for each questions are indicated against it

ii. Question no. 1 to 5 are very short-answer questions, carrying 1 mark each. Answer these in one word or about one sentence each.

iii. Question no. 6 to 12 are short answer questions, carrying 2 marks each. Answer these in about 30 words each.

iv. Question no. 13 to 24 are short answer question of 3 marks each. Answer these in about 40 words each.

v. Question no. 25-27 are long answer questions of 5 marks each. Answer these in about 70 words each.

vi. Supply proper diagram in support of your answer

vii. Use Log Tables, if necessary. Use of calculators is not permitted

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1. If three elements A, B and C crystallize in a cubic solid lattice with A atoms at the corner, B atoms at the cube center and C atoms at the edges, then what is the formulae of the crystal?

2. How can colloidal solution of sulphur in water be prepared?

3. Out of Cr ²⁺ and Cr ³⁺ which is more stable and why?

4. Give the IUPAC name of Na₃[Co(NO₂)]?

5. An isotope of an element is present in group 18 and 5 th period of the periodic table. What will be the position occupied by its daughter element in the periodic table if it emits one ? particle per atom?

6. Calculate the wavelength of an object moving with a velocity of 3 X 10 ⁴ m/sec given the mass of object = 6 x 10 ^-24 kg.

7. Explain why the bond order of N₂ is greater than N₂⁺; but the bond order of O₂ is less than O₂⁺?

8. Calculate the value of Avogadro constant from the following data: Density of NaCl = 2.165 gm/ cu.cm. Distance between Na and Cl ion in NaCl =281 pm.

9. 1.00 gm of a nonelectrolyte solute dissolved in 50.5 gm of benzene lowered the freezing point of the benzene by 0.40 K . The freezing point depression constant of benzene is 5.12 K kg / mol. Find the molecular mass of the solute and the atomicity of the molecule, if the atomic mass of the solute is 32

10. State the third law of thermodynamics and its implication

11. How would you explain the sharp increase in molar conductivity of a weak electrolyte on dilution? How is the molar conductivity related to the degree of dissociation of a sparingly soluble salt?

12. Write the balanced equation for the following reactions:

a. Ca₃P₂ + water

b. P₄ + KOH + water

13. The Quantised energy of electron in hydrogen atom for the nth energy level is given by: E_n = -13.12 x 10 ⁵ / n² J per mole Calculate the minimum energy required to remove the electron completely from hydrogen atom when its quantised energy level n equals 2. What should be the wavelength of light the can be used to cause this transition?

14. Aluminium crystallises in a cubic close packed structure. Its metallic radius is 125 pm.

a. What is the length of the side of the unit cell

b. How many unit cells are there in 1.00 cubic cm of Aluminium

15. Two elements A and B form compounds having molecular formula AB₂ and AB₄ When dissolved in 20 gm. Of benzene 1 gm of AB₂ lowers the freezing point by 2.3 K, while 1.0 gm of AB₄ lowers it by 1.3 K The molar depression constant for benzene is 5.1 Kg per mole Calculate the atomic mass of A and B?

16. A reaction is first order in A and second order with respect to B:

a. Write differential rate equation

b. How is the rated affected if the concentration of B is tripled

c. How is the rate effected when the concentration of both A and B are doubled

17. The activation energy of a reaction is 75.2 Kj/mole in the absence of a catalyst and 50.14 kj/mole in presentce of the catalyst. How many times will the rate of reaction grow in the presence of the catalyst if the reaction proceeds at 25^oC? (R=8.314 J/K/mole)

18. Explain the term:

a. Electrophoresis

b. Coagulation

c. Tyndall effect

19. Give reason for each of the following observation:

a. Noble gases are mostly chemically inert

b. Nitrogen does not form pentahalide

c. Bismuth is a strong oxidising agent in pentavalent state

20. Account for the following:

a. Ni ⁺² ion is thermodynamically more stable than Pb ²⁺.

b. Transition metals forms a number of interstitial compounds.

c. Silver halide founds use in photography

21. Describe the preperation of Potassium Dichromate from chromite ore with chemical equation and the structure of dichromate ion.

22. Draw a sketch to show the splitting of d-orbitals in an octahedral crystal field. State for a d⁶ ion how the actual configuration of the split d-orbitals in an octahedral crystal field is decided by the relative values of ?o and P.

23. a. How can the course of a reaction be known by using radioisotopes.

c. Describe the principle of breeder reactor.

d. Complete the following equation: …….(?,2n) ²¹¹At₈₅.

24. a. Identify and indicate the presence of center of chirality, if any, in the following molecules: i. 2-aminobutane ii. 1,2-dichloropropane

b. Employing Cahn-Ingold-Prelog sequence rule indicate the priority sequence: -methyl, -ethyl, -isopropyl, - terbutyl.

25. Explain the following statement:

a. Sulphur exhibits greater tendency for catenation than selenium

b. Tin (II) is a reducing agent where as Pb (II) is oxidising agent.

c. Silicon is an insulator but silicon doped with phosphorous acts as a semi-conductor.

d. Trisilyl ammine is planar but trimethylammine is pyramidal.

e. PH₃ is weaker base than NH₃.

Or//

a. Assign a reason for the following statements:

i. SF₆ is easily hydrolysed.

ii. In solid PCl₅ exists as an ionic compound

iii. CO₂ and SiO₂ are not isostructural.

b. Arrange the following in the decreasing order of the property indicated

i. H₂O, H₂S, H₂Se, H₂Te -- boiling point

ii. F,Cl, Br, and I --- Bond energy

26. a. Predict the product of electrolysis in the following:

i. An aqueous solution of silver nitrate with silver electrodes

ii. A dilute solution of sulfuric acid with platinum electrodes

iii. An aqueous solution of CuCl₂ with platinum electrodes.

b. The resistance of a conductivity cell containing 0.001 M KCl solution at 298 K is 1500 ohm. What is the cell constant if the conductivity of 0.001 M KCl solution at 298 K is 0.146 x 10 ^-3 S/cm

27. a. Give reason:

i. Many thermodynamically feasible reactions do not occur under ordinary condition.

ii. An exothermic reaction is sometimes not spontaneous.

b. The standard Gibbs energy Change values at 1773 K are given for the following reactions: 4 Fe + 3 O₂ 2Fe₂O₃ G = -1487 Kj/mole

4 Al + 3 O₂ 2 Al₂O₃ G = -22500 Kj/mole

2 CO + O₂ 2CO₂ G= -515Kj/mole Find out the possibility of reducing Fe₂O₃ and Al₂O₃ with CO at this temperature.