Board Paper of Class 12-Science 2012 Chemistry (SET 1) - 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 2
What
is the role of graphite in the electrometallurgy of aluminium?
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- Question 5
Draw
the structural formula of 2-methylpropan-2-ol molecule.
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- Question 6
Arrange
the following compounds in an increasing order of their reactivity in
nucleophilic addition reactions: ethanol, propanal, propanone,
butanone.
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- Question 7
Arrange
the following in the decreasing order of their basic strength in
aqueous solutions:
CH3NH2,
(CH3)2NH, (CH3)3 N and
NH3
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- Question 8
Define
the term, ‘homopolymerisation’ giving an example.
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- Question 9
A
1.00 molal aqueous solution of trichloroacetic acid (CCl3COOH)
is heated to its boiling point. The solution has the boiling point of
100.18°C. Determine the van’t Hoff factor for
trichloroacetic acid. (Kb for water = 0.512 kg mol−1)
OR
Define
the following terms:
(i)
Mole fraction
(ii)
Isotonic solutions
(iii)
Van’t Hoff factor
(iv)
Ideal solution
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- Question 10
What
do you understand by the ‘order of a reaction’? Identify
the reaction order from each of the following units of reaction rate
constant:
(i)
L−1 mol s−1
(ii)
L mol−1 s−1
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- Question 11
Name
the two groups into which phenomenon of catalysis can be divided.
Give an example of each group with the chemical equation involved.
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- Question 12
What
is meant by coagulation of a colloidal solution? Describe briefly any
three methods by which coagulation of lyophobic sols can be carried
out.
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- Question 13
Describe
the principle involved in each of the following processes.
(i)
Mond process for refining of Nickel.
(ii)
Column chromatography for purification of rare elements.
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- Question 14
Explain
the following giving an appropriate reason in each case.
(i)
O2 and F2 both stabilize higher oxidation
states of metals but O2 exceeds F2 in doing so.
(ii)
Structures of Xenon fluorides cannot be explained by Valence Bond
approach.
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- Question 16
What
is meant by (i) peptide linkage (ii) biocatalysts?
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- Question 17
Write
any two reactions of glucose which cannot be explained by the open
chain structure of glucose molecule.
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- Question 18
Draw
the structure of the monomer for each of the following polymers:
(i)
Nylon 6
(ii)
Polypropene
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- Question 19
Tungsten
crystallizes in body centred cubic unit cell. If the edge of the unit
cell is 316.5 pm, what is the radius of tungsten atom?
OR
Iron
has a body centred cubic unit cell with a cell dimension of 286.65
pm. The density of iron is 7.874 g cm−3. Use this
information to calculate Avogadro’s number (At. Mass of Fe =
55.845 u)
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- Question 20
Calculate
the amount of KCl which must be added to 1 kg of water so that
the freezing point is depressed by 2K. (Kf for water =
1.86 K kg mol−1)
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- Question 21
For
the reaction
2NO(g)
+ Cl2(g) → 2 NOCl(g)
The
following data were collected. All the measurements were taken at 263
K:
Experiment
No.
|
Initial
[NO] (M)
|
Initial
[Cl2] (M)
|
Initial
rate of disappearance of Cl2 (M/min)
|
1
|
0.15
|
0.15
|
0.60
|
2
|
0.15
|
0.30
|
1.20
|
3
|
0.30
|
0.15
|
2.40
|
4
|
0.25
|
0.25
|
?
|
(a)
Write the expression for rate law.
(b)
Calculate the value of rate constant and specify its units.
(c)
What is the initial rate of disappearance of Cl2 in
exp. 4?
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- Question 22
How
would you account for the following?
(i)
Many of the transition elements are known to form interstitial
compounds.
(ii)The
metallic radii of the third (5d) series of transition
metals are virtually the same as those of the corresponding
group member of the second (4d) series.
(iii)Lanthanoids
from primarily +3 ions, while the actinoids usually have
higher oxidation states in their compounds, +4 or even + 6 being
typical.
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- Question 23
Give
the formula of each of the following coordination entities:
(i)
Co3+ ion is bound to one Cl−, one
NH3 molecule and two bidentate ethylene diamine (en)
molecules.
(ii)
Ni2+ ion is bound to two water molecules and two oxalate
ions.
Write
the name and magnetic behaviour of each of the above coordination
entities.
(At.
nos. Co = 27, Ni = 28)
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- Question 24
Although
chlorine is an electron withdrawing group, yet it is ortho-,
para-directing in electrophilic aromatic substitution reactions.
Explain why it is so?
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- Question 25
Draw
the structure and name the product formed if the following alcohols
are oxidized. Assume that an excess of oxidizing agent is used.
(i)
CH3CH2CH2CH2OH
(ii)
2-butenol
(iii)
2-methyl-1-proponal
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- Question 26
Write
chemical equation for the following conversions:
(i)
Nitrobenzene to benzoic acid.
(ii)
Benzyl chloride to 2-phenylethanamine.
(iii)
Aniline to benzyl alcohol.
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- Question 27
What
are the following substances? Give one example of each one of them.
(i)
Tranquilizers
(ii)
Food preservatives
(iii)
Synthetic detergents
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- Question 28
(a)
What type of a battery is the lead storage battery? Write the anode
and the cathode reactions and the overall reaction occurring in a
lead storage battery when current is drawn from it.
(b)
In the button cell, widely used in watches, the following reaction
takes place
Determine
E° and ΔG°
for the reaction
OR
(a)
Define molar conductivity of a solution and explain how molar
conductivity changes with change in concentration of solution for a
weak and a strong electrolyte.
(b)
The resistance of a conductivity cell containing 0.001 M KCl solution
at 298 K is 1500Ω.
What is the cell constant if the conductivity of 0.001 M KCl solution
at 298 K is 0.146 × 10−3
S cm−1?
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- Question 29
(a)
Complete the following chemical reactions equations:
(i)
(ii)
(b)
Predict the shape and the asked angle (90° or more or less) in
each of the following cases:
(i)
and
the angle O − S − O
(ii)
ClF3 and the angle F − Cl − F
(iii)
XeF2 and the angle F − Xe − F
OR
(a)
Complete the following chemical equations:
(i)
(ii)
(b)
Draw the structures of the following molecules:
(i)
H3PO2
(ii)
H2S2O7
(iii)
XeOF4
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- Question 30
(a)
Illustrate the following name reaction giving suitable example in
each case:
(i)
Clemmensen reduction
(ii)
Hell-Volhard-Zelinsky reaction
(b)
How are the following conversions carried out?
(i)
Ethylcyanide to ethanoic acid
(ii)
Butan-1-ol to butanoic acid
(iii)
Benzoic acid to m-bromobenzoic acid
OR
(a)
Illustrate the following reactions giving a suitable example for
each.
(i)
Cross aldol condensation
(ii)
Decarboxylation
(b)
Give simple tests to distinguish between the following pairs of
compounds
(i)
Pentan-2-one and Pentan-3-one
(ii)
Benzaldehyde and Acetophenone
(iii)
Phenol and Benzoic acid
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