Sample Paper 2012 Class XII Subject Chemistry s1

Sample Paper – 2012 Class – XII Subject – Chemistry

Time-3 hrs M.M- 70

GENERAL INSTRUCTIONS: 1 All questions are compulsory. 2.Question number 1 to 8 are very short answerquestions,carry 1 mark each 3.Question number 9 to 18 are short answer questions,carry 2 marks each 4 Qquestions number 19 to 27 are also short answer questions,carry 3 marks each. 5 Question number 28 to 30 are long answer questions carry 5 marks 1.What is the difference between ionic bond and metallic bond ? 2. Why does conductivity decrease with dilution ? 3. Comment on the statement that “colloid is not a substance but a state of substance”. 4.Why nitrogen is gas and phosphorous is solid ?. 5.Write IUPAC name of the following compound: CH3CH2CH(CH3)CH(C2H5)Cl 6.Draw structure of 2-(2-Chlorophenyl)-1-iodooctane 7.Define peptide bond of protein ? 8.Discuss the main purpose of vulcanisation of rubber 9.Why non ideal solution shows negative deviation?Explain with example ? OR What type of deviation is observed when n-heptane is added to ethanol ?Explain ? 10.Explain a method to prevent corrosion ? 11 Calculate the potential of hydrogen electrode in contact with a solution whose pH is 10. 12. Answer the following: (i) PH3 has lower boiling point than NH3. Why?

(ii) Why is BiH3 the strongest reducing agent amongst? 13 On what ground can you say that scandium (Z = 21) is a transition element but zinc (Z = 30) is not? 14 (i) Why is sulphuric acid not used during the reaction of alcohols with KI? (II) Why Grignard reagents should be prepared under anhydrous conditions? 15. Convert- (i) Benzyl chloride → Benzyl alcohol (ii) Methyl magnesium bromide →2-Methylpropan-2-ol 16. Explain (i) pKb of aniline is more than that of methylamine. (ii). Aniline does not undergo Friedel-Crafts reaction 17. Explain with one example (i) Hofmann’s bromamide reaction (ii) Diazotisation 18. Explain the difference between Buna-N and Buna-S.? (2) 19. Aluminium crystallises in a cubic close-packed structure. Its metallic radius is 125 pm. (i) What is the length of the side of the unit cell? (ii) How many unit cells are there in 1.00 cm3 of aluminium?? (3) 20. A sample of drinking water was found to be severely contaminated with chloroform (CHCl3, M.mass=119.5) supposed to be a carcinogen. The level of contamination was 15 ppm (by mass): (i) express this in percent by mass (ii) determine the molality of chloroform in the water sample. (3) OR Two elements A and B form compounds having formula AB2 and AB4. When dissolved in 20 g of benzene (C6H6), 1 g of AB2 lowers the freezing point by 2.3 K whereas 1.0 g of AB4 lowers it by 1.3 K. The molar depression constant for benzene is 5.1 K kg mol–1. Calculate atomic masses of A and B. (3) 21.(i). What are enzymes ? Write in brief the mechanism of enzyme catalysis. ? (ii) What are emulsions? What are their different types? (iii) Describe some features of catalysis by zeolites. (3) 22. Explain-: (i) Describe a method for refining nickel? (ii) How is ‘cast iron’ different from ‘pig iron”? (iii) What is the significance of leaching in the extraction of aluminium.(3) 23.Explain giving reason- (i) Why do the transition elements exhibit higher enthalpies of atomisation? ? (ii) For the first row transition metals the Eo values have irregular trend. Why ? (iii) Explain why Cu+ ion is not stable in aqueous solutions? 2– 24. (i) Why [NiCl4] is paramagnetic.? (ii) Why aqueous copper sulphate solution (blue in colour) gives a green precipitate with aqueous potassium fluoride. (iii) Draw figure to show the splitting of d orbitals in an octahedral crystal field. 25.. (a)Why cannot vitamin C be stored in our body? (b)What products would be formed when a nucleotide from DNA containing thymine is hydrolysed? (c )When RNA is hydrolysed, there is no relationship among the quantities of different bases obtained. What does this fact suggest about the structure of RNA? 26. Describe the following: (i) Acetylation (ii) Cannizzaro reaction (iii) Decarboxylation 27. Explain the following terms with suitable examples (i) cationic detergents (ii) anionic detergents and (iii) non-ionic detergents

28 (a) The decomposition of N2O5 in CCl4 at 318K has been studied . Initially the –1 –1 concentration of N2O5 is 2.33 mol L and after 184 minutes, it is reduced to 2.08 mol L . The reaction takes place according to the equation

2 N2O5 (g) → 4 NO2 (g) + O2 (g) Calculate the average rate of this reaction ? What is the rate of production of NO2 during this period? (3) (b) The rate constant for a first order reaction is 60 s–1. How much time will it take to reduce the initial concentration of the reactant to its 1/16th value? (2)  29.Assign reason for the following: 1x5 (i) Why does O3 act as a powerful oxidising agent? (ii) Which form of sulphur shows paramagnetic behaviour and why ? (iii) What happens when sulphur dioxide is passed through an aqueous solution of Fe(III) salt? (iv) Sea is the greatest source of some halogens. Comment. (v) What inspired N. Bartlett for carrying out reaction between Xe and PtF6? 30.(a)An organic compound with the molecular formula C9H10O forms 2,4-DNP derivative reduces Tollens’ reagent and undergoes Cannizzaro reaction. On vigorous oxidation, it gives 1,2-benzenedicarboxylic acid. Identify the compound(3) (b) Give simple chemical tests to distinguish between the Phenol and Propanol ? (1) (c ) Write the mechanism of hydration of ethene. (1) Sample Paper – 2013 Class – XII Subject – Chemistry (Theory)

Time allowed: 3 hrs M.Marks: 70

General Instructions:

1. Name two antidepressants. 1 2. Define 12-16 compounds. 1 3. . Define the pseudomolecular reactions. 1 4. Give one example of sulphonation reaction.

5. Write IUPAC name of CH3-CH=CH-CH2- CHO 1 6. Draw the structure of zwitter ion. 1 7. Convert Benzene to flurobenzene. 1 8. What are biodegradable polymers? Give one example. 1 9. What are Antifertility drugs? Give examples. 10. Define colligative properties with example. 11. A 1st order reaction is 50% complete in 30 minutes at 270C and in 10 min. at 470C.Calculate (i) rate constant for reaction at 270C and 470C. (ii) energy of activation for the reaction.

12. What is activation energy? How is it related to rate constant K? 2

13. Give four differences between types of emulsions. 2 14. What are lyophobic colloids? Give two examples. How does lyophobic colloid differ from lyphillic colloids. 2

15. Compare the stability of +2 oxidation state of elements with outer electronic configuration 3d64s2,3d54s2 and 3d34s2 in aqueous solution. 2 OR What is Lanthanoid Contraction? Mention two consequences of Lanthanoid contraction. 2

16. Explain the mechanism of dehydration of alcohols. 2

17. Distinguish chemically between a) phenol and ethanol b) methanal and ethanal. 2

18. Write the equation of the reaction involved in the preparation of Bakelite. 2

19. Al crystallizes in a cubic close packing structure (FCC) Its metallic radius is 125 pm .Find the edge length of the unit cell. How many unit cells are there in 1cm3 of Al ? How many atoms are there in 1cm3 of Al ?

20. Calculate the boiling point of 1M KCl solution. Density of solution=1.04g/cm3. 3 Molar mass of KCl=74.5u Kb=0.52K Kg mole-1.Assume KCl is 90% dissociated in aqueous solution.

21. Give the structures of a) XeO3 b) H3PO4 c) PCl3 3

22. Account for the following: 3 a) Zn,Cd, and Hg are not considered as transition elements. b) Actinoid show variety of oxidation states. c) Transition metals forms alloys.

23. a) Write main postulates of werner,s co-ordination theory.

b) Draw the geometrical isomers of [Co(NH3)3(NO2)3] OR

What type of isomerism is exhibited by [Co(NH3)5Br]CO3? Write the IUPAC name of both the isomers. Give one chemical test to distinguish between these two isomers. 3

24. Explain SN1 and SN2 Reactions. 3 25. Outline the principles of refining of the metals by the following methods: 3 a) Mond’s process b) Liquation c) distillation.

26. Explain following: 3 a) williamson’s reaction. b) wurtz reaction. c) schotten-baumann reaction.

27. i) Explain the following with respect to protein- a) Native state of protein b) Peptide linkage 3 ii) Two strands of DNA are not identical but complimentary to each other. Explain this statement.

28. a) Write the reaction involved at each electrode in H2-O2 fuel cell. 5 b) Give one similarity and one difference between fuel cell and other primary cells. c) Give advantages of fuel cells. OR a) State Kohlrausch law of independent migration of ions. 5 b) Write the reaction involved at each electrode in mercury cell / dry cell. c) Calculate the cell potential at 298K for the reaction Zn+Sn4+ Zn2+ +Sn2+ (1.5M) 0.5M) (2M) E0Zn2+/Zn= - 0.76V E0Sn4+/Sn2+= 0.13V

29. a) Account for the following: 5 i) Group 18 elements have positive value of electron gain enthalpy.

ii) HF has highest boiling point while HCl has the lowest boiling point among hydrogen halide. iii) Sulphur vapours are paramagnetic in naturte.

b) Give the products and balance the reactions:

i) Cu + H2SO4 (conc) ii) XeF4+ H2O OR a) Account for the following: 5

i) NeF2 is not known.

ii) Fluorine has lesser negative value of electron gain enthalpy than Chlorine.

b) explain Ostwald’s process. 30. a) Carry out the following conversions: 5 i) Benzene to fluorobenzene..

ii) Benzaldeyde to 3-Phenyl propan-1-ol

iii) Benzoic acid to m-nitro benzoic acid.

b) Give one example each of i) Stephen reduction ii) Aldol condensation. OR a) Explain LUCAS test for distinguish between 10 20 and 30 alcohols. b) Give one example each of i) Cannizaro reaction ii)Acetylation. SAMPLE PAPER 2013 SUB: CHEMISTRY CLASS- XII TIME :3 Hr M.M 70  ------ GENERAL INSTRUCTIONS----- ( ACCORDING TO BOARD)

Q-1 Out of c and co which is better reducing agent for ZnO? Q-2 what is the role of NaCN in froth floation method? Q-3 what is F centre? Q-4 what are antioxidants? Q-5 why AgBr shows both frenkel and schottky defect? Q-6 Name the initiator used in free radical polymerization. Q-7 What is the effect of tem on adsorption? Q-8 what are monomer units of nylon6,6 Q-9 Differentiate b/w ----(1)bactericidal & bacteriostatic antibiotic drugs (2) Disinfectant &antiseptic Q-10 What is the difference b/w schottky and frenkel defect? Q-11 What is the chemical reaction of------(a) lead storage battery (b) Ni/Cd battery

Q-12 [a] Arrange the following in increasing value of Kb—C6H5NH2,C2H5NH2,(C2H5NH)2,NH3

[b] Arrange the following in increasing order of B.P C2H5OH,C2H5NH2, (CH3)2NH Q-13 Write the mechanism of formation of ethane from ethanol. Q-14 What is lanthanod contraction ?write its concequences. Q-15 What is ELLINGHAM DIAGRAM explain with diagram. Q-16 Give Reason –1.Acylation of aniline is necessary before nitration. 2.Why o-nitrophenol is more volatile than p-nitrophenol? Q-17 Draw the structure of ----1.amylopectin 2. Maltose Q-18 [a] What is instantaneous rate of reaction? [b] The conversion of molecule X to Y follows second order kinetics. If concentration of X increased to three times how will it affect the rate of formation. Q-19 In thermal power station shahjahanpur coal is bernt to produce steam for electricity. The smoke produce gets precipited in the chemnies having precipitator Answer the following 1.why is the smoke passed through precipitator ? 2. How does coal ash affect atomosphere? 3. Which value is promoted through the use of electrostatic precipitator Q-20 Define the following terms [a] Zwitter ion [b] peptide bond [c] broad spectrum antibiotics Q- 21 calculate the cell potential of [1] Zn/Zn++//Cu++/Cu, [2]Cr/Cr+++(0.1M)//Fe++(0.01M)/Fe Given that E0Cr+++/Cr=-0.75v, Eo Fe++/Fe=-0.45v E0Zn/zn++=0.76v, Eo Cu++/Cu=-0.34v Q-22 complete the following

1. NH3+Cl2(EXCESS)------→

2. SIO2+HF ------→

3. H3PO3 ------→ Q-23 [a]With the help of V.B.T explain the magnetic character & shape of NI( CN)4

[b] Write the I.U.P.A.C name of [Cr(NH3)(H2O)3]Cl2

Q-24 Draw the structure of (a) chromate ion (b) manganate ion (c) XeO2F2 Q-25 Carry out following conversions 1. Prop-1-ene to propan-2-ol 2. Methanamine to ethanamine 3. Chlorobenzene to D.D.T Q-26 Answer the following questions 1. Why soda water bottle fizzes out on opening the cap 2. How sea water is purified 3. What is raoults law Q-27 1.EXPLAIN WITH CHEMICAL REACTION A. Rosenmund reduction B. Carbyl amine reaction.. C. Hoffmann’s reaction 2.Distinguish b/w following pairs A. Phenol & benzoic acid B.propan-2-ol propan -1-ol

Q-28 [A] Determine the amount of CaCl2(i=2.47) dissolved in 2.5 litre of water such that its osmotic pressure is 0.75atm at 27OC [B] Write chemical reaction occurring in [1] Bessemer converter [2]Blast furnace Q-29 An organic compound ‘A’ on treatment with aqueous solution of ammonia and heating forms compound ‘B’ which on heating with Br2 and KOH forms a compound ‘C’ of molecular formula C6H7N. Write structure of &I.U.P.A.C names of A, B, & C. Write chemical reactions involved. Q-30 Arrange the following according to given instructions [A] HCLO4,HCLO3,HCLO2,HCLO (INCREASING ACIDIC STRENGTH)

[B]F2, Cl2, Br2, I2 (INCREASING BOND DISSOCIATION ENERGY)

[C]NH3, PH3, AsH3, SbH3, BiH3 INCREASING BASIC CHARACTER) [d]HF, HCl , HBr HI ( INCREASING ACIDC ARACTER) [E]H2O , H2S , H2Se ,H2Te ( THERMAL STABILITY)