CBSE Class XII Model Paper of Chemistry (Model Papers) 2012
1. Point defect Decreases the density of a crystal? (1)
2. What is the primary structural feature necessary for a molecule to make it useful in a condeusation pdymesisation reaction? (1)
3. What is the number of atoms in a unit cell of FCC crystal? (1)
4. Arrange the following compaunds in an increasing order of basic strength in their aqueaus solutions (1)
NH3 , CH3NH2 , (CH3)2 NH , (CH3)3 N
5. Write the IUPAC name of (CH3)2 CH-CH2,-C-CH(CH3)2 (1)
6. Why is electrolytic reduction preferred over chemical reduction for the isolation of certain metals? (1)
7. What is the role of depressant in froth floatation process? (1)
8. What is the percentage efficiency of packing in case of a metal crystal for body centred cubic structure? (1)
9. A copper-silver cell is set up. The copper ion concentration in it is 0.10 M the silverion canc. is not known. the cell potential mearured 0.422 V. Determine the conc. of silver ion in the cell, Given E0Ag+=0.80v, E0cu2+/cu=+0.34v (2)
10. Describe the role of the following :- (2)
(i.) NaCN in the extraction of silver from a silver ore
(ii.) Cryolite in the extraction of aluninium from pure alumina
11. Differentiate between condensation and addition polymerisation. Give one example each of the resulting polymers. (2)
12. Explain the mechanism of aid dehyhration of ethanol to yield ethene. (2)
13. Draw the structures of (i) Xef2 (ii)H3Po4 (2)
(i) Rusting of iron in saline water
(ii) Iron does not rust even if zinc coating is broken
14. Describe the following with on example of each. (2)
(i) Reimer-Themann Reaction
(ii) Sandmeyer Reaction
Describe the follwing reactions with one example of each
(i) Friedal- Craft reaction
(ii) Cannizzaro Reaction
15. Complete the following chemical reaction equations (2)
16. Complete the following chemical reaction equation:- (2)
(i) MNO4+ C2O42-+ H+
(ii) Cr2O72-+ Fe2++ H+
17. Enumerate the reactions and facts of D-glucose which cannot be explained by its open chain structure. (2)
18. A first order reaction has a rate constant of 0.0051 min-1 If we begin with O.10M Canc. of reactant, What conc. of the reactant will be left after 3 hours. (2)
19. Calculate the cell emf and Drgo for the following at 25oc Zn(s)/Zn2+(0.1M) 11 Cd2+ (0.01M)/ Cd(s) Given EoZn2+/Cd=-0.763 Volt, 1F=96500 C mol-1, R=8.314 JK-1 Mol-1
Calculate the standard electrode potential of Ni2+/Ni electrode if emf of the cell Ni(s)/Ni2+/Ni2+(0.01 m)II Cu2+ (0.1M)I Cu(s) is 0.59volt Given Eo Cu2+/Cu = +0.34 Volt
20. Explain the following
(i) Electrophoresis (ii) Dialysis (iii) Tyndall effect
21. (i) What is spectro chemical series 1×3=3
(ii) Show the splitting of degenerate d-crbitals occarding to crystal field theory.
(iii) How the configuration of d-orbitals is decided on the basis of pairing energy?
22. Explain the following observations :-
(i) These are two -NH2 groups in semi carbazide but only one is involved in the formation of semicarbazone
(ii) Phenols are more acidic than alcohols
(iii) Alkyl halider when react with alcohlic KOH, forms alkenes.
23. Give reason for the following observation :-
(i) Of the d4 species, Cr2+ is strongly reducing where as Mn (III) is strongly oxidising.
(ii) The enthalpies of atomization of the transition metals are quite high.
(iii) Interstitial compounds are well known for transition metals.
24. Compound a C6H12O2 on reduction with liA2H4 yields two compounds B and C. The compound B On oxidation gave D which on treatment with aqueous alkali and subsequent heating furnished E. The latter on catalytic hydrogenation gave C. The compound D on further oxidation gave CH3COOH Deduce the structure of A,B,C,D and E.
25. Define the following and give one example of each
(i) Antihistamine (ii) Antacids (iii) Antibiotics
26. Calculate the freezing point of a solution containing 18 g glucose C6H12O6 and 68.4 g sucrose C12H22011 in 200g of water the freezing point of pure water is 273 K and Kf for water is 1.86 K Kg mol-1
What conc of nitrogen should be present in a glass of water at room temperature? Assume a temperature of 25oC, a total pressuse of 1 atm and mole fraction of nitrogen in air of 0.78 (KH for nitrogen=8.42X10-7M/mm Hg)
27. The half life for a first order reaction is 5 x 104s. What percentage of the initial reactant will react in 2 hours. (3)
28. (a) Draw the structure of (i) H2S2O8 (ii) HCLO4 (2+3)
(b) How would you account for the following :
(i) NH3 is a stronger base than PH3
(ii) Sulphur has a greater tendency for catenation than oxygen.
(iii) F2 is a stronger oxidising agent than Cl2
(b) Arrange the following in the increasing order of property indicated.
(i) H-F H-Cl H-Br H-I acidic nature.
(ii) NH3< /sub> PH3 AsH3 SbH3 B1H5 Basic nature.
(iii) H2O H2S H2Se H2Te H2Po Boiling point.
29. (a) Write the chemical reaction to illustrate the following : (2+3)
(i) Rosenmund reduction (ii) Aldol condensation.
(b) Distinguish between the following pairs :
(i) Propanal and propanone
(ii) Acetophenone and Benzophenone
(iii) Phenol and Benzoic acid.
(a) Convert the following
(i) Ethanol to 3-hydroxybutanal
(ii) Benzaldehyde to Benzophenone
(b) An Organic compound A has the molecular formula C8H16O2 It gets hydrolysed with dil sulphuric acid and gives a carboxylic acid B and on alcohol C. C,on oxidation with chromic acid also produced B C on dehydration given but-1end write equation for the reactions involved.
30. (i) Write the preporation of potassium permanganate crystals from its ore. How KMnO4 act as an oxidising agent in acidic medium
(ii) What happens when acidic KMNO+ reacts with a (a)HI (b) FeSo4 (c) C2H2O4
(i) Write the preparation of potassium dichromate is crystals for its are.
(ii) What happens when potassium dichromate is treated with acid and with base.
(iii) Draw the structure of chromate and dichromate ion.
(iv) Write the ionic equation when potassium dichromate reacts with SnCl2 and with FeCl2 in acidic medium.
(a.) What are transition elements? What is the difference between the electronic configurations of transition and inner transition elements?
By:- Amar Ujala
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