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SAMPLE PAPER -10
CLASS-XII
SUB - CHEMISTRY
Time Allowed: 3 Hrs
Maximum Marks: 70
General Instructions:
1. All questions are compulsory.
2. Question No. 1-8 are very short answer questions and carry 1 mark each.
3. Question No. 9-18 are short answer questions and carry 2 marks each.
4. Question No. 19-27 are also short answer questions and carry 3 marks each.
5. Question No. 28-30 are long answer questions and carry 5 marks each.
6. Use log tables if necessary, use of calculators is not allowed.
1. Why is the bond dissociation energy of fluorine molecule less than that of chlorine molecule?
2. What is meant by shape selective catalysis?
3. Write the IUPAC name of CH3CO CH2CH=CH COOH.
4. Is optical isomerism possible in tetrahedral complex? Why?
5. What do you mean by order of reaction?
6. How are phenols much more acidic than alcohols?
7. What are reducing sugars?
8. Give the use of DDT, Freon 12 .
9. Aluminium crystallizes in a fcc closed packed structure. Its atomic radius is 12.5 pm.
(a) What is the length of the edge of the unit cell?
(b) How many such unit cells are there in a 2.00 m3 piece of aluminium.
10. Give reasons:
(a)Aromatic amines are less basic than aliphatic amines.
(b)Aniline does not undergo Friedel Crafts alkylation
11. (a) Write IUPAC name of the following:
(i)K3 [Fe (C2O4)3]
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(ii)Pt (NH3)6] Cl4.
(b)What are ambidentate ligands ? Explain with example.
12. (a)Give the resonating structures of NO2 & N2O5 .
(b)Complete the following reactions:
(i) 4Al + 3O2 →
(ii)C2H4 + O2
OR
Write the steps involved in Contact’s process
13. For the reaction:
NO2 (g) + CO2 (g) → CO2 (g) + NO(g)
The proposed mechanism is as below:
(a)NO2+NO2→NO+NO3 (slow)
(b)NO3+CO→CO2+NO2 (fast)
What is the rate law for the reaction?
14. How will you distinguish between:
(a)(CH3)2NH & (CH3)3N
(b)C6H5NH2 & CH3NH2
15. Account for the following observation:
(a) Among the halogens, fluorine is the strongest oxidizing agent.
(b) Acidity of oxoacids of chlorine is HOCl< HOClO<HOClO2 <HOClO3
16. Define ferro magnetism (ii) anti ferromagnetism
17. (a) Explain the terms strong and weak electrolyte.
(b) Calculate the emf of the cell:
Mg(s) /Mg2+ (0.1M)║Cu2+(1x10-3M)/ Cu(s)
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18. The rate of a particular reaction doubles when temperature changes from 270C to 370C.
Calculate the activation energy of such reaction.
19. Describe the following with suitable example:
(a)Transquilizers
(b) Preservatives
(c) Analgesics.
20. (a) What are fuel cells? Write the electrode reaction of a fuel cell which uses the reaction of
hydrogen with oxygen.
(b) Write the formulation and the standard cell potential of the galvanic cell in which the
following reaction takes place: Fe2+(aq)+ Ag+(aq) →Fe3+(aq) +Ag(s)
21. How are the following conversions carried out?
(a) Phenol to acetophenone
(b) Ethanol to 2-propanol
22. (a)Differentiate between roasting and calcinations. Explain with example.
(b) Why is copper matte roasted in a reverberatory furnace lined inside with silica?
23. Which alkyl halide from the following pairs reacts more rapidly by SN2 mechanism? Explain
it.
(a) CH3-CH (CH3)-CH2CH2Br
(I)
or
CH3CH2-CH (CH3)-CH2Br
(II)
(b)CH 3CH 2CH 2CH 2Br
or CH 2CH 2CH(Br) CH3
(I)
(c) CH3CH2CH(Br)CH3
(II)
or CH3CH(CH3)2Br
(I)
(II)
24. (a)Explain the principle of electrodialysis.
(b) In NH3 and CO2, which gas will be absorbed more rapidly on the surface of charcoal and
why?
(c)How are multimolecular colloids different from macromolecular colloids?
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25. Differentiate between addition and condensation polymers based on mode polymerization.
Give one example of each.
OR
Wite the monomers of
i) PVC (ii) Teflon (iii) nylon-6
26. Give reasons
(a) interhalogen compounds are more reactive than halogens.
(b)PCl5 is known but NCl5 is not known.
(c) Amongst all noble gases only xenon is known to form compounds with oxygen and
fluorine.
27. Nita’s mother fell ill & doctor diagnosed her with pernicious anemia. She felt lethargic and
her mother in household work till she recovered.
i)
ii)
iii)
Name the vitamin whose deficiency caused pernicious anemia.
Name the sources which will provide this vitamin.
Mention the values shown by Nita
28. (a) Assign reason for the following:
(i)Transition metal ions are usually coloured.
(ii) Transition elements exhibit variable oxidation state.
(iii) Interstitial compounds are well known for transition metal.
(b) Give balanced chemical equation of the two reactions in which KMnO4 acts as an
oxidizing agent in acidic medium.
OR
Give reasons for the following:
a) Transition metals have high enthalpies of atomization.
b) Among the lanthanoids, Ce(III) is easily oxidised to Ce(IV).
c) Fe3+/Fe2+ redox couple has less positive electrode potential than Mn3+/Mn2+couple.
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d) Copper (I) has d10 configuration, while copper (II) has d9 configuration, still copper (II) is
more stable in aqueous solution than copper (I).
e) The second and third transition series elements have almost similar atomic radii.
29. (a) Account for the following:
(i) Electrophilic substitution in benzoic acid takes place at meta position.
(ii)Carboxylic acids have higher boiling points than alcohols of comparable molecular
mass.
(b)How will you bring about the following conversions?
(i)Propanone to Propene
(ii) Benzoic acid to Benzaldehyde
(iii) Ethanol to 3-hydroxybutenal.
OR
a) How are the following preparations carried out?
i) 2- Butenal from ethanal
ii) Tert - Butyl alcohol from acetone
b) Give the mechanism of HCN addition to acetaldehyde
c) Write chemical equations to illustrate each of the following reaction:
i) Acylation reaction
ii) Rosenmund reaction
30. What is meant by Van’t Hoff factor?
The osmotic pressure of 0.0103 molar solution of an electrolyte is found to be 0.70 atm at 270C.
Calculate the Van’t Hoff factor. [R=0.082 Later mol-1K-1]. What conclusion do you draw about
the molecular state of the solute in the solution?
OR
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a) Vapour pressure of CCl4 at 250C is 143 mm of Hg. 0.5g of a non volatile solute(molar
mass 65)is dissolved in 100 ml CCl4. Find the vapour pressure of the solution.(Density of
CCl4 = 1.58g/cm3)
b) State Henry’s law. Give its two practical applications.
SAMPLE PAPER -10
SCORING KEY
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1. (a) Lower value of bond dissociation energy of F 2 is due to strong repulsion between the non
bonding elements of F atom in F2 molecule.( 1)
(b)Due to the absence of the d- orbitals, multiple bonding cannot occour(1).
2. Shape selective catalysis is a chemical reaction in which the rate depends on the pore size of
catalyst and also on the shape and size of the reactant and product molecule(1).
3. 5-oxohex-2-enoicacid. (1).
4. No. because all 4 bonds are symmetrically placed and equivalents
5. Order of the reaction may be defined as “the sum of powers or exponents of the reactants in
the rate of law expression (1).
6. Phenol is more acidic than alcohol because after losing H+ ion, it forms the phenoxide ion
which is resonance stabilized. On the other hand, in methoxide ion, no resonance is possible
(1).
7. All these carbohydrates which reduce the Fehling solution and Tollens reagent are referred
to as reducing sugar. Eg. All monosaccharides like Lactose, Maltose are reducing sugar (1).
8. (a) Freon 12: It is used as aerosol propellants, refrigeration and air conditioner purposes.
(b) DDT: It is used as insecticide. (1)
9. (a) It crystallizes in a cubic closed packed structure.
Therefore, length of the side of the cube= 2√2r
=2√2 x 1.25 x 10-8 cm
=3.53 x 10-8 cm
=353.6 pm.
(1)
(b) Volume of the unit cell = (3.53 x 10-8) 3 = 4.398 x 10-23 cm3
Therefore, number of unit cells present in 1 cm3 of Al
=1/4.398 x 1023 = 2.27 x 1022 unit cell.(1)
10. (a) Aromatic amines are less basic than alphatic amines because in the former, lone pair of
nitrogen is involved in the conjugation due to resonance. Thus, the availability of lone pair of
donation decreases and acts as weak base. (1)
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(b) Aniline reacts withAlCl 3 a lewis acid to form salt. Hence, it does not undergo Fridel
Crafts alkylation (1).
11. (a) Potassium trioxalatoferate (III)(1)
(b) Hexaamine platinum (IV) chloride.(1)
12.Correct structures (1/2 +1/2).
OR
S + O2→ S O2
S O2+ O2→ S O3
S O3 + H2SO4 →H2 S 2O7
H2 S 2O7 + H2O→ H2SO4
13. The slowest step of the reaction is: NO2 + NO2 → NO + NO3 (1)
Hence, the rate of reaction is:
Rate= K [NO2] [NO2]
= K [NO2]2 (1)
14. (a)
Secondary Amine [(CH3)2NH]
Secondary amine gives insoluble substance
with benzene sulphonyl chloride which
remains unaffected on addition of acid.
Tertiary Amine [(CH3)3N
Tertiary amine does not react with benzene
sulphonyl chloride and remains insoluble in
alkali and can be dissolved in acid.
(b)
Primary Amine(CH3NH2)
Does not give dye test
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Aromatic Amine (C6H5NH2)
Aromatic amines produces yellow coloured
azodye when it is treated with benzene
diazonium chloride..
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15. (a) The electrode potential of F2 is maximum, which is why it is the strongest oxidizing
agent(1).
(b) Explanation with resonating structures.(1)
16. Correct definitions
17. (a) (i) Strong electrolyte: Those electrolytes which dissociate completely into ions are called
strong electrolytes. Eg. NaOH, HCl, NaCl etc.(1/2)
(ii) Weak electrolyte: Those electrolytes which do not ionize completely in aqueous
solution or in molten state are called weak electrolytes. Eg. H2CO3, CH3COOH, etc.(1/2)
(b)Cu/Cu2+ (aq)║Mg2+ (aq)/Mg
E0 Cell =-2.37-(+0.34)=-2.71V. (1)
18. log K2 /K1=Ea /2.303R [1/T1 -1/T2]
Log2=Ea x10 /2.303x8.314x300 x310
(1/2)
(1/2)
Ea =0.3010 x2.302 x8.314x300x310/10 (1/2)
=53598.6J mol-1
(
(1/2)
19. (a) Transquilizers: The chemical substances used to cure mental diseases are called
transquilizers. They reduce anxiety and tension. Eg. Calmpose, veronal etc.(1)
(b)Preservatives: Chemical substances which are added to food to improve itsshelf life,
appearance, taste and food value are called preservatives. Eg. Sodium benzoate.
C6H5COONa.(1)
(c) Analgesics: Those drugs which relieve or decrease pain are termed as analgesics. Eg.
Analgin, etc.(1)
20. (a)Fuel cell: Electrical cells which are designated to convert the energy from combustion of
fuels such as H2, or CH4 directly into electrical energy are called fuel cell. In this cell, the
hydrogen and oxygen are bubbled through a porous carbon electrode into concentrated
aqueous NaOH(1)
At anode:
2H2(g)+ 4OH- (aq)→ 4H2O(l) +4e
At cathode:
O2(g) + 2H2O(l) +4e →4OH_(aq)
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Overallreaction:O2(g) +2H2(g)→2H2O(l)
(b)Fe2+ (aq) +Ag+((aq)→Fe3+(aq) +Ag(s)
E0Ag/Ag =0.80v, E0Fe/Fe=0.77v.
E0cell=E0Cathode-E0Anode
=0.80-0.77=0.03V (1)
G0= -nFE
=2x96500x0.03=5790J/mol =5.790Kj/m0l(1).
21. Phenol to Acetophenone
( a )C6H5-OH + ( CH3CO)2O→C6H5( OCOCH3)+AlCl3→C6H4(OH) (OCOCH3)+Zn
Distill→C6H5(COCH3)(1)
(b)C2H5OH+[O]→CH3CHO+CH3MgBr/H2O→ (CH3)2CHOH
(1)
(a) C6H5NH2+diasotisation→C6H5N2Cl+boiling water→C6H5OH (1)
22. Calcination involves heating when volatile matter escapes leaving behind the metal oxide.
Eg: ZnCO3 (s)
→
ZnO(s)+CO2(g)
(1)
Roasting the ore is heating it in presence of regular supply of air at high temperature below its
melting point.
Eg: 2PbS+3O2 →
2PbO +2SO2
(1)
(b) To remove the iron oxide as iron silicate
FeO +SiO2 → FeSiO3
(1)
23. Structure (I)undergo SN2 reaction (1)
(b) Structure (I) UndergoSN2reaction because it is primary halide (1)
(c) Structure (I) undergo SN2reaction faster because it is secondary halide and structure (II)is
tertiary halide(1)
24. (a)It is based on the principle that the ions pass through the parchment membrane fsster in
the electric field .(1)
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(b)NH3 will be absorbed more readily because it has higher critical temperature. (1)
(c)Multimolecular colloids consists of aggregation of small molecules or atoms.eg;sulphur sol.
Macromolecular colloids consists of macromlecules ie polymers; eg starchsol..
25. Two differences (2)
One example each (1).
OR
i) vinyl chloride ii) tetra fluoro ethene (iii) caprolactum
26. (a)X-X’ bond present in inter halogen compounds is weaker than the X-X bonds present in
halogens. (1)
(b) d-orbital is present in phosphorous while it absent in nitrogen(1)
(c)Because of large size and low ionization enthalpy.(1).
27. i) Vitamin B12
(ii) Yeast, milk
(iii) Concern and love for her mother
28. (a) (i) Due to d-d transition.(1)
(ii) Because the energy of(n-1)d orbital and ns orbitals are of coparable energy.
(iii) Because of small size of their atoms other small atoms can be easily trapped in the
interstitial space.(1)
(b) 2KMnO4+5C2H2O4+3H2SO4→K2SO4+2MnSO4+10CO2 +8H2O (1)
Or ionic equation
2KMnO4 +5SO2 +2H2O→K2SO4 +2MnSO4 +2H2SO4 (1)
OR
a) Are held by strong inter atomic forces. Explain.
b) Ce(IV) is quite stable due to 4f0 configuration. Explain.
c) Mn2+ has 3d5 configuration explain.
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d) Cu(1) is not stable due to its less negative enthalpy of hydration than Cu(II).
e) Due to lanthanoid contraction, the increase in radii of second to third transition series
almost vanishes.
29. (a) (i)due to resonance stabilization of of benzoic acid meta position becomes electron
rich.(1)
(ii)Strong hydrogen bonding in benzoic acid.(1)
(b)(i)CH3COCH3+[H]/Ni→CH3CH(OH)CH3+Con.H2SO4→CH3CH=CH2(1)
(ii)C6H5COOH+SOCl2→C6H5COCl +H2 /PdBaSO4 →C6H5CHO (1)
(iii)2CH3CH2OH +Mild oxidation (KMnO4 )→2CH3OH +NaOH→CH3CH3 (OH)CH2CHO (1)
OR
a) i) Aldol condensation; give the equation.
ii) Acetone is treated with methyl magnesium bromide followed by hydrolysis. Equation.
b) Mechanism
c) i) The reaction of aceyl halide with acides, amines etc. give
equation.
ii) Reduction of acid halide with Pd and BaSO4 to form aldehyde.
30. Vant Hoff’s factor-correct definition and equation (1+1)
╖=ICRT (1)
0.70=ix0.0i03 x0.082 x (27+273) (1)
I=0.70/0.0103 x0.082x300=2.76 (1)
OR
W2= 0.5g
M2= 65amu
W1= 100X1.58=158g
P01-P1 W2 M1
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----- = -----P01 M2 W1
0.5X154
P1= 143 - -------- X 143
65X158
=142 mm of Hg.
b) Henry’s law m=KHP
Application: i) bends, (ii) anoxia
SAMPLE PAPER -10
Blue Print
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Unit
No.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
Unit
VSA(1)
The Solid State
Solutions
Electrochemistry
Chemical Kinetics
Surface Chemistry
General Principles & Processes of isolation of elements
p - Block Elements
d & f elements
Co - ordination Compounds
Haloalkanes & Haloarenes
Alcohols, Phenols & ethers
Aldehydes, Ketones & Carboxylic acids
Amines
Biomolecules
Polymers
Chemistry in everday life
SA(3)
LA(5)
2
1
1
1
1
1
2
2
1
1
1
1
1
1
1
1
1
1
1
1
1
2
1
8
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SA(2)
1
10
1
1
9
3
Page 14
Total
70
4
5
5
5
4
3
8
5
3
4
4
6
4
4
3
3
70