Board Paper of Class 12-Science 2011 Chemistry (SET 3) - Solutions
General Instructions:
(i) All questions are compulsory
(ii) Question numbers 1 to 8 are very short-answer questions and carry 1 mark each.
(iii) Question numbers 9 to 18 are short-answer questions and carry 2 marks each.
(iv) Question numbers 19 to 27 are also short-answer questions and carry 3 marks.
(v) Question numbers 28 to 30 are long-answer questions and carry 5 marks each.
(vi) Use Log Tables, if necessary. Use of calculators is not allowed.
- Question 1
‘Crystalline
solids are anisotropic in nature’. What does this statement
mean?
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- Question 2
Express
the relation among the conductivity of solution in the cell, the cell
constant and the resistance of solution in the cell.
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- Question 5
Arrange the following compounds in an increasing order of their solubility in water:
C6H5NH2, (C2H5)2NH, C2H5NH2
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- Question 6
Write the IUPAC name of the following compound:
(CH3)3 CCH2Br
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- Question 8
In
nylon 6, 6 what does the designation ‘6, 6’ mean?
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- Question 9
What type of a battery is lead storage battery? Write the anode and the cathode reactions and the overall reactions occurring in a lead storage battery.
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- Question 10
Two
half-reactions of an electrochemical cell are given below:
Construct
the redox equation from the standard potential of the cell and
predict it the reaction is reactant favoured or product favoured.
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- Question 11
State reasons for each of the following:
(i) The N − O bond in is shorter than the N − O bond in
(ii) SF6 is kinetically an inert substance.
OR
State reasons for each of the following:
(i) All the P-Cl bonds in PCl5 molecule are not equivalent.
(ii) Sulphur has greater tendency for catenation than oxygen.
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- Question 12
Distinguish between ‘rate expression’ and ‘rate constant’ of a reaction.
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- Question 13
Assign reasons for each of the following:
(i) Transition metals generally form coloured compounds.
(ii) Manganese exhibits the highest oxidation state of +7 among the 3d series of transition elements.
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- Question 14
How would you obtain
(i) Picric acid (2, 4, 6-trinitrophenol) from phenol,
(ii) 2-Methylpropene from 2-methylpropanol?
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- Question 15
Explain the following giving one example for each:
(i) Reimer-Tiemann reaction.
(ii) Friedel Craft’s acetylation of anisole.
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- Question 16
Describe
what you understand by primary structure and secondary structure of
proteins.
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- Question 17
What
is essentially the difference between α-form of glucose and
β-form
of glucose? Explain.
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- Question 18
Name
the sub-groups into which polymers are classified on the basis of
magnitude of intermolecular forces.
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- Question 19
The density of lead is 11.35 g cm−3 and the metal crystallizes with fcc unit cell. Estimate the radius of lead atom (At. Mass of lead = 207 g mol−1 and NA = 6.02 × 1023 mol−1)
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- Question 20
Explain
how the phenomenon of adsorption finds application in each of the
following processes:
(i)
Production
of vacuum
(ii)
Heterogeneous
catalysis
(iii)
Froth Floatation process
OR
Define
each of the following terms:
(i)
Micelles
(ii)
Peptization
(iii)
Desorption
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- Question 21
Nitrogen pentoxide decomposes according to equation: 2N2O5(g) → 4NO2(g) + O2(g)
This first order reaction was allowed to proceed at 40° C and the data below were collected:
[N2O5] (M) |
Time (min) |
0.400 |
0.00 |
0.289 |
20.0 |
0.209 |
40.0 |
0.151 |
60.0 |
0.109 |
80.0 |
(a) Calculate the rate constant. Include units with your answer.
(b) What will be the concentration of N2O5 after 100 minutes?
(c) Calculate the initial rate of reaction.
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- Question 22
Complete
the following chemical equations:
(i)
(ii)
(iii)
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- Question 23
Write the name, stereochemistry and magnetic behaviour of the following:
(At. nos. Mn = 25, Co = 27, Ni = 28)
(i) K4[Mn(CN)6]
(ii) [Co(NH3)5Cl]Cl2
(iii) K2[Ni(CN)4]
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- Question 24
Describe
the principle behind each of the following processes:
(i)
Vapour phase refining of a metal.
(ii)
Electrolytic refining of a metal.
(iii)
Recovery of silver after silver ore was leached with NaCN.
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- Question 25
Answer the following:
(i) Haloalkanes easily dissolve in organic solvents, why?
(ii) What is known as a racemic mixture? Give an example.
(iii) Of the two bromoderivatives, C6H5CH(CH3)Br and C6H5CH(C6H5)Br, which one is more reactive in substitution reaction and why?
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- Question 26
Complete the following chemical equations:
(i)
(ii) C6H5N2Cl + H3PO2 + H2O →
(iii)
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- Question 27
Answer the following questions:
(i) Why do soaps not work in hard water?
(ii) What are the main constituents of dettol?
(iii) How do antiseptics differ from disinfectants?
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- Question 28
(a) Give chemical tests to distinguish between
(i) Propanal and propanone,
(ii) Benzaldehyde and acetophenone.
(b) How would you obtain
(i) But-2-enal from ethanal,
(ii) Butanoic acid from butanol,
(iii) Benzoic acid from ethylbenzene?
OR
(a) Describe the following giving linked chemical equations:
(i) Cannizzaro reaction
(ii) Decarboxylation
(b) Complete the following chemical equations:
(i)
(ii)
(iii)
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- Question 29
(a) Explain the following:
(i) NF3 is an exothermic compound whereas NCl3 is not.
(ii) F2 is most reactive of all the four common halogens.
(b) Complete the following chemical equations:
(i) C + H2SO4 (conc) →
(ii) P4 + NaOH + H2O →
(iii)
OR
(a) Account for the following:
(i) The acidic strength decreases in the order HCl > H2S > PH3
(ii) Tendency to form pentahalides decreases down the group in group 15 of the periodic table.
(b) Complete the following chemical equations:
(i) P4 + SO2Cl2 →
(ii) XeF2 + H2O →
(iii)
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- Question 30
(a) Differentiate between molarity and molality for a solution. How does a change in temperature influence their values?
(b) Calculate the freezing point of an aqueous solution containing 10.50 g of MgBr2 in 200 g of water. (Molar mass of MgBr2 = 184 g) (Kf for water = 1.86 K kg mol−1)
OR
(a) Define the terms osmosis and osmotic pressure. Is the osmotic pressure of a solution a colligative property? Explain.
(b) Calculate the boiling point of a solution prepared by adding 15.00 g of NaCl to 250.0 g of water. (Kb for water = 0.512 K kg mol−1), (Molar mass of NaCl = 58.44 g)
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