Board Paper of Class 12-Science 2006 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
A
cubic solid is made of two elements X and Y. Atoms Y
are at the corners of the cube and X at the body centre. What is the
formula of the compound?
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- Question 2
Two
liquids A and B boil at 145°C and 190°C respectively. Which
of them has a higher vapour pressure at 80°C?
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- Question 3
For
the reaction A → B, the rate of reaction becomes twenty seven
times when the concentration of A is increased three times. What is
the order of the reaction?
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- Question 5
Give
a chemical test to distinguish between aniline and N-methyl aniline.
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- Question 6
(a) Draw
the structure of XeF2
molecule.
(b) Write
the outer electronic configuration of Cr atom (Z = 24).
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- Question 7
What is meant by entropy-driven reaction? How can a reaction with positive changes of enthalpy and entropy be made entropy driven?
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- Question 8
Write
balanced chemical equations for the following reactions:
(i) Ca3P2
+ H2O
→
(ii) XeF6
+ 3 H2O
→
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- Question 9
Write
chemical equations of
the reactions involved in the manufacture of potassium permanganate
from pyrolusite ore.
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- Question 10
What are enantiomers? Draw the structures of the possible enantiomers of 3-methyl pent-1-ene.
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- Question 11
Write
the reactions and the conditions involved in the conversion of:
(a) Propene
to 1-Propanol
(b) Phenol
to Salicylic acid
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- Question 12
Write
the structures of monomers used in the preparation of:
(a) Teflon
(b) PMMA
Or
(a) How
does vulcanisation change the character of natural rubber?
(b) Why
are the numbers 66 and 6 put in the names of nylon-66 and nylon-6?
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- Question 13
State Heisenberg’s uncertainty principle. An electron has a velocity of 50 ms−1 accurate up to 99.99%. Calculate the uncertainty in locating its position? (Mass of electron = 9.1 ×10−31kg, h= 6.6 ×10−34 Js).
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- Question 14
An
element has a body-centred
cubic structure with a cell edge of 288 pm. The density of the
element is 7.2 g cm−3
Calculate the number of atoms present in 208 g of the element.
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- Question 15
(a) Why
is the vapour pressure of a solution of glucose in water lower than
that of water?
(b) A
6.90 M solution of KOH in water contains 30% by mass of KOH.
Calculate the density of the KOH solution?
[Molar mass of KOH = 56
g mol −1]
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- Question 16
Answer the following in brief:
(a) Which of the two isomers of butane is more stable at 25°C and why?
Given [n-butane (ΔfH 0= −120 kJ mol−1) and iso-butane (ΔfH0= −130 kJ mol−1)]
(b) For the change H2O (l) →H2O (g), predict the sign of ΔS.
(c) For the reaction N2(g) + 3H2(g) → 2NH3(g), predict whether work is done by the system or on the system and why?
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- Question 17
The
rate of a particular reaction triples when temperature changes from
50°C to 100°C. Calculate the activation energy of the
reaction.
[log
3 = 0.4771; R = 8.314 J K
−1
mol−I]
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- Question 18
(a) How
can a colloidal solution and true solution of the same colour be
distinguished from each other?
(b) List
four applications of adsorption.
Or
Explain
the following observations:
(a) Lyophilic
colloid is more stable than lyophobic
colloid.
(b) Coagulation
takes place when sodium chloride solution is added to a colloidal
solution of ferric hydroxide.
(c) Sky
appears blue in colour.
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- Question 19
Name
the chief ore of silver. Describe with chemical equations the
extraction of silver from this ore.
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- Question 20
(a) Using
valence bond theory predict the geometry and magnetic behaviour of
[Cr (NH3)6]3+
ion [Cr = 24].
(b) Write
IUPAC name of:
[Pt
(NH 3)2Cl2]
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- Question 21
(a) The
isotope of
decays
in 14 steps, by loss of 8 α-particles
and 6 β-
particles. What are the mass number and atomic number of the end
product?
(b) Write
the equation for the complete reaction
(D,
α).
(c) How
is the nuclear binding energy related to the stability of the
nucleus?
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- Question 22
(a) Describe
the following giving suitable examples:
(i) Cannizzaro
reaction
(ii) Aldol
condensation
(b) Give
a chemical test to distinguish between ethanal and propanal.
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- Question 23
Account
for the following:
(a) Electrophilic
substitution in case of aromatic amines takes place more readily than
benzene.
(b) CH3CONH2
is a weaker base than CH3CH2NH2.
(c) Nitro
compounds have higher boiling points than hydrocarbons having almost
same molecular mass.
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- Question 24
Define
the following and give one example of each:
(a) Tranquillisers
(b) Mordant
(c) Hybrid
rocket propellants
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- Question 25
(a) Explain
why electrolysis of aqueous solution of NaCl gives H2
at cathode and Cl2
at anode. Write overall reaction.
(b) Calculate
the emf of the cell Zn/Zn2+
(0.1
M) || Cd2+
(0.01 M)/Cd at 298 K, [Given
and
Or
(a) Account
for the following:
(i) Alkaline
medium inhibits the rusting of iron.
(ii) Iron
does not rust even if the zinc coating is broken in a galvanised iron
pipe.
(b)
(i) Construct
a galvanic cell using the above data.
(ii) For
what concentration of Ag +
ions will the emf of the cell be zero at 25°C, if the
concentration of Cu2+
is 0.01 M?
[log 3.919 = 0.593]
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- Question 26
Give
reasons for the following:
(a) Molten
aluminium bromide
is poor conductor of electricity.
(b) Nitric
oxide becomes brown when released in air.
(c) PCl5
is ionic in nature in the solid state.
(d) Ammonia
acts as a ligand.
(e) Sulphur
disappears when boiled with an aqueous solution of sodium sulphite.
Or
Name
the principal ore of tin or lead. Describe the different steps (along
with equations for the reactions) involved in the extraction of the
metal from the ore named. Name an important alloy of each, tin and
lead.
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- Question 27
(a) State
two main differences between globular proteins and fibrous proteins.
(b) Based
on their chemical composition, state how are lipids classified? Give
one example of each class.
Or
(a) ‘Hormones
are chemical messengers.’ Explain?
(b) Name
the main disease caused due to lack of the vitamin and its source in
each of the following: A, B6
and E.
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