CLASS – XII
Time: Three Hours Max. Marks: 70
All questions are compulsory.
Q. Nos. 1 to 8 are very short answer questions and carry 1 mark each.
Q. Nos. 9 to 18 are short answer questions and carry 2 marks each.
Q. Nos. 19 to 27 are also short answer questions and carry 3 marks each.
Q. Nos. 28 to 30 are long answer questions and carry 5 marks each.
Use log tables if necessary, use of calculators not allowed.
1. A reaction is 2A + B 2D and rate law is found to be Rate = k [A]3/2 What is order and molecularity of reaction? (1)
2. H3PO3 is diprotic. Why? (1)
3. How many moles of vacant cationic sites will be there if NaCl crystal is doped with 2x10-10 mole Indium Chloride? (1)
4. For the following reaction, 4NH3 (g) + 5O2 (g) 4NO (g) + 6H2O (g) . write the rate of formation of ‘NO’ in terms of concentration of ammonia. (1)
5. Write IUPAC name of compound CH3 NH CH3 (1)
7. Arrange the following halides in order of increasing reactivity through SN2 mechanism. (1)
CH3CH2Br, CH3Br, (CH3)3CBr, (CH3)2CHBr.
8. Write the change that occurs in the structure of protein when raw egg is boiled. (1)
9. What will be the effect of temperature on the adsorption of a gas on solid in case of physisorption and chemisorption? (2)
10. What happens when (2)
I. Electric current is passed through ferric hydroxide sol.
II. Freshly prepared precipitate of AgCl is agitated with aqueous solution of silver nitrate.
11. An element (density 6.8 g cm-3) occurs in BCC structure with cell edge of 280 pm. Calculate the number of atoms presents in 250 gm of element. (2)
12. The graphical representation of the variation of m vs. for two electrolytes AB and PQ was found as below (2)
I. Write the nature of electrolytes AB and PQ.
II. Write the effect of dilution on the dissociation of AB.
13. Write the chemical reactions in which sulphuric acid acts as (2)
I. Dehydrating agent
II. Oxidizing agent
14. Why is o-nitro phenol more acidic than phenol but less acidic than p-nitro phenol? Explain. (2)
15. Write the mechanism of formation of diethyl ether from ethanol.
Write Williamson’s synthesis process for preparation of methoxy ethane? Write one important advantage of this method.
16. How will you distinguish between (2)
I. Benzyl amine and aniline.
II. Secondary amine and tertiary amine.
17. A colourless crystalline solid C7H6O2 on heating with PCl5 gives a compound ‘A’ which on Rosenmund reduction gives a compound ‘B’. Further oxidation of ‘B’ gives out original crystalline solid. (2)
a) Identify A and B.
b) Write the chemical reactions involved in the formation of A and B.
18. Arrange the following compounds in the increasing order of property indicated. (2)
a) HBr, HF, HCl, HI (acidic strength).
b) HClO3, HClO, HClO4, HClO2 (stability).
19. Write the chemical reaction that occurs during (3)
I. Preparation of Al by electrolytic reduction of Alumina.
II. Refining of Nickel by Mond’s process.
III. Extraction of Ag by leaching with NaCN.
20. How is Xenon hexafluoride prepared? Draw its structure and write the type of hybridization. (3)
21. Explain the following citing one example (3) . I. 1. Analgesics
I. 2.Broad spectrum antibiotics
II. 3. Anti histamines
What are antimicrobials? Give one example. Write the three ways of controlling a microbial disease.
22. (a) What is Lanthanide contraction? Write its two consequences. (2)
(b) Transition metals form coloured compounds. Why? (1)
23. What are fuel cells? Write the reaction taking place at anode and cathode in Hydrogen-oxygen fuel cell with brief explanation. (3)
24. The following experimental data was collected for the reaction at 298K . (3)
Cl2 (g) +2NO (g) 2NOCl (g)
21.6 x 10-4
a) Write the rate law for above reaction.
b) Determine the rate constant.
c) Calculate the rate of reaction when concentration of Cl2 (g) and NO (g) are 0.015 and 0.025 mol l-1 respectively.
25. (a) Write the names of two components of starch. How do they differ in (3)
I. Structural unit.
II. Solubility in water
Explain the following in case of DNA
II. Replication (iii) Transcription
26. (a) What are co-polymers? Give one example. (1)
(b) How is PVC manufactured? What is the role of benzoyl peroxide in polymerization of vinyl chloride? (2)
27. How will you convert (3)
I. Isopropyl chloride into propene
II. Phenol into o-bromophenol
III. Aniline into benzoic acid.
28. (a) What is Henry’s Law? Write its two limitations. (2)
(b) What is osmosis? Average osmotic pressure of human blood is 7.4 atm at 270C. Calculate total concentration of various solutes present in the blood. Assuming this concentration in molality, calculate the freezing point of blood.
(Kf =1.86 Kg molal-1, R =0.0821 l atm K-1 mol-1) (3)
a) What is abnormal molecular mass? Write the value of Vant Hoff factor for benzoic acid dissolved in benzene. (2)
b) Two liquids X and Y on mixing form ideal solution. The vapour pressure of solution containing 3 mol of X and 1 mol of Y is 550 mm of Hg. But when 4 mol of X and 1 mol of Y are mixed the vapour pressure is 560 mm of Hg. Calculate the vapour pressure of pure X and Y. (3)
29. (a) Account for the following (2)
I. Chloro acetic acid is stronger than acetic acid.
II. Ethanamide has higher boiling point than ethanoic acid.
III. Aniline does not undergo Friedal and Craft reaction.
(b) Write IUPAC name of following (3)
I. (CH3)3 C-CHCl-CH3
30. (a) What are geometrical isomers? Represent the geometrical isomer of
Co (en)2Cl2 + ion. (2)
(b) Out of two complexes Fe (CN)6 3-and Fe(CN)6 4- which one is more stable and why ? (1)
(c) Give reasons (1+1)
I. Ce4+ ion is more stable than Ce2+.
II. KMnO4 solution is decolourised by acidified solution of oxalic acid.
A series of organic reaction is represented as below. (2+2+1)
A Conc HNO3 +H2SO4 B Sn/HCl C NaNO2 + HCl D HOH
278 K Boil
a) Identify A, B, C and D.
b) Write the complete chemical reaction for each step.
c) Write the type of reaction changing C into D.
Prepared and presented by:-
C.D. Ram, Vice Principal
K.V. OEF Hazratpur