Board Paper of Class 12-Science 2007 Chemistry (SET 1) - Solutions
General Instructions:
(i) All questions are compulsory.
(ii) This question paper consists of four sections A, B, C and D.
Section A contains 5 questions of one mark each.
Section B is of 7 questions of two marks each.
Section C is of 12 questions of three marks each and
Section D is of 3 questions of five marks each.
(iii) There is no overall choice. However, an internal choice has been provided.
(iv) Wherever necessary, the diagrams drawn should be neat and properly labelled.
- Question 1
What
is the number of atoms per unit cell in a body-centred
cubic structure?
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- Question 3
For
the reaction
the
rate law is expressed as
rate
= k[Cl2][NO]2
What
is the overall order of this reaction?
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- Question 5
Why
do nitro compounds have high boiling points in comparison with other
compounds
of same molecular mass?
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- Question 6
State
‘Pauli’s exclusion principle’. Explain giving an
example how this principle limits the maximum occupancy of an energy
level in an atom.
OR
State
‘Aufbau principle’ and give the order in which the
energies of orbitals increase and hence they are filled in that
order.
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- Question 7
A reaction with, always has an equilibrium constant value greater than 1. Why?
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- Question 8
Write
balanced chemical equations for
the following reactions:
(i)
Aluminium dissolves in aqueous hydrochloric acid
(ii)
Tin reacts with a hot alkali solution
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- Question 9
Write
the structures
of the following species:
(i)
H3PO2
(ii) H2SO5
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- Question 10
Identify whether the following pairs of compounds are structural or geometrical isomers:
(i)
(ii)
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- Question 11
How
would you account
for the following:
(i)
Phenols are much more acidic than alcohols.
(ii) The boiling points of
ethers are much lower than those of the alcohols of comparable molar
masses.
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- Question 12
Draw
the structure of the monomer of each of the following polymers:
(i) Polyvinylchloride (PVC)
(ii) Nylon-6
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- Question 13
Write the molecular orbital configurations of the following species and rearrange them in the increasing order of their bond lengths:
and O2.
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- Question 14
Explain
each of the following with a suitable example:
(i)
Paramagnetism
(ii)
Piezoelectric effect
(iii)
Frenkel defect in crystals
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- Question 15
In the production of water gas the reaction involved is:
C(s) + H2O(g) →CO(g) + H2(g), ΔrH°= +131.4 kJ mol−1
For this reaction, ΔrS°is +134 JK−1mol−1. Find out the spontaneous feasibility of this reaction at (i) 25°C and (ii) 1000°C.
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- Question 16
An
antifreeze solution is prepared from 222.6 g of ethylene glycol
[C2H4(OH)2]
and 200 g of water. Calculate the molality of the solution. If the
density of this solution be 1.072 g mL−1,
what will be the molarity of the solution?
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- Question 17
The
decomposition of NH3
on platinum surface,
is
a zero order reaction with k
= 2.5 × 10−4
M s−1.
What are the rates of production of N2
and H2?
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- Question 18
Explain
the following terms giving a suitable example in each case:
(i)
Emulsification
(ii)
Homogeneous catalysis
OR
Define
adsorption. Write any two features which distinguish physisorption
from chemisorption.
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- Question 19
How
would
you account for the following?
(i) The lower oxidation state
becomes more stable with increasing atomic number in Group 13.
(ii)
Hydrogen fluoride is much less volatile than hydrogen chloride.
(iii)
Interhalogen compounds are strong oxidising agents.
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- Question 20
Write the name and draw the
structure of each of the following complex compounds:
(i) [Co(NH3)4
(H2O)2]Cl3
(ii) [Pt(NH3)4]
[NiCl4]
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- Question 21
The net nuclear reaction of a
radioactive decay series is written as:
Write
three pieces of information that you get from the above equation.
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- Question 22
Give
chemical tests to distinguish between the following pairs of
compounds:
(i)
Propanal and propanone
(ii)
Methyl acetate and ethyl acetate
(iii)
Benzaldehyde and benzoic
acid
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- Question 23
How
would you achieve
the following conversions:
(i)
Nitrobenzene to aniline
(ii)
An alkyl halide to a quaternary ammonium salt
(iii)
Aniline to benzonitrile
Write
the chemical equation with reaction conditions in each case.
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- Question 24
(i)
Give an example of a hybrid propellant.
(ii)
What are acid dyes?
(iii)
Name a food preservative which is most commonly used by food
producers.
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- Question 25
(a) Describe
the general trends in the following properties of the first series of
the transition elements:
(i) Stability of +2 oxidation
state
(ii) Formation of oxometal ions
(b) Assign reason for each of
the following:
(i) Transition elements exhibit
variable oxidation states
(ii) Transition metal ions are
usually coloured
OR
(a) Write the steps involved in
the preparation of:
(i)
K2Cr2O7
from Na2CrO4
(ii)
KMnO4
from K2MnO4
(iii) Calomel from corrosive
sublimate
(b) What is meant by lanthanoid
contraction? What effect does it have on the chemistry of the
elements which follow lanthanoids?
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- Question 26
(a)
Calculate the emf of the cell
Mg(s)
| Mg2+
(0.1M)
|| Cu2+
(1 × 10−3
M) | Cu (s)
Given:
E°
Cu2+/Cu
= +0.34V, E° Mg2+/Mg
= −2.37 V
(b)
Explain with examples the terms weak and strong electrolytes.
OR
(a) The
resistance of a conductivity cell containing 0.001 M KC1 solution at
298 K is 1500 Ω.
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?
(b)
Predict the products of electrolysis in the following:
A solution of
H2SO4
with platinum electrodes.
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- Question 27
(a) Name the
three major classes of carbohydrates and give an example of each of
these classes.
(b)
Answer the following:
(i) What type of linkage is
responsible for the primary structure of proteins?
(ii) Name the location where
protein synthesis occurs in our body.
OR
(a)
How are lipids classified? Give an example of each class.
(b)
Explain the following terms:
(i) Mutarotation
(ii) Avitaminosis
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