CHEMISTRY (Theory) sample paper 3 Class – XI
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December 18, 2015 |
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CHEMISTRY (Theory)
Class – XI
Time allowed: 3 hours Maximum
Marks: 70
General
Instructions:
a) All the questions are
compulsory.
b) There are 26
questions
in total.
c) Questions 1
to
5 are very short answer type questions and
carry one mark each.
d) Questions 6
to
10 carry two marks each.
e) Questions 11
to
22 carry three marks each.
f) Questions 23
is
value based question carrying four marks.
g) Questions 24
to
26 carry five marks each.
h) There is no overall choice.
However, an internal choice has been provided in one question of
two marks, one question of three
marks and all three questions in five marks each. You have
to attempt only one of the
choices in such questions.
i) Use of calculators is not
permitted.
However, you may use log tables if necessary.
1. Why the molar enthalpy of
vapourisation of acetone is less than that of water?
2. How many electrons are present
in 16g of methane?
3. How many grams of Na2CO3
should
be dissolved to make 100 cc of 0.15M Na2CO3?
4. What will be the volume of ammonia
formed if 2L of nitrogen is mixed with 2L of hydrogen at constant temperature and
pressure?
5. Give two examples of state
functions.
6. a) Is it possible to achieve
equilibrium between water and its vapour in an open vessel?
b) Explain your answer and say
what happens eventually.
7. How does electronegativity
vary i) down the group and ii) across the period?
8. The standard solution of NaOH
cannot be prepared by weighing. Why?
9. Give reason: “Although
geometries of ammonia and water molecules are distorted tetrahedral, bond angle in water is less than
that of ammonia”.
Or
Why is benzene extra-ordinary
stable though it contains three double bonds?
10. In the estimation of sulphur
by Carius method, 0.468 g of an organic sulphur compound afforded 0.668 g of barium sulphate. Find out the percentage of sulphur in
the given compound.
11. What happens when
alkali metals reacts in air?
12. Give the Lewis
representation of:
i. Nitric acid
ii. Ammonia
iii. Ozone molecule
13. In the reaction: 2 2 3 2SO
(g) + O ⇌2SO
(g) + 189.4 kJ
Indicate the
direction in which the equilibrium will shift when:
i) Concentration of
SO2 is increased.
ii) Concentration of
SO3 is increased.
iii) Temperature is
increased.
14. Calculate the wavelength in nm, of visible light
having a frequency of 4.37 x 10-14/s.
15. Comment on each
of the following observations:
a) Lithium forms a
nitride directly like magnesium. Give equation involved.
b) BaO is soluble but
BaSO4 is insoluble in water.
16. Give
reasons: “The reaction 2 Na(s) + H2 (g)
_ 2 NaH (s) is a redox change”.
17. Give reason:
(i) Graphite is used
as lubricant.
(ii) Diamond is used
as an abrasive.
(iii) Aluminium
alloys are used to make aircraft body.
Or
Explain isomerization
in alkanes with examples.
18. An alkyl halide
compound ‘A’ (C5H11Br) reacts with ethanolic KOH to give compound ‘B’,
an
alkene. ‘B’ on
reaction with bromine gives compound ‘C’. ‘C’ on further dehydrobromination
gives compound ‘D’.
When one mole of ‘D’ is treated with sodium metal in liquid ammonia, it
gives one mole of
sodium salt of ‘D’ and half a mole of hydrogen gas. On complete
hydrogenation, ‘D’
gives a straight reactions involved.
19. Calculate the
amount of ammonia formed when 50 kg of N2 (g)
and 10.0 kg H2 (g) of are mixed to
produce NH3 (g). Identify the limiting reagent.
20. Give reasons:
i. Evaporation causes
cooling.
ii. Falling liquids
drops are spherical.
iii. Vapour pressure of acetone is less than that of
ether at same temperature.
21. Give a note on:
i. Mist
ii. Smoke
iii. Fumes
iv. Dust
22. Calculate the
enthalpy change when 2.38g of CO vaporizes at its normal boiling point, if the enthalpy of
vaporization of CO is 6.04 kJ/mol.
23. John
takes snacks every day to school, but Mala takes vegetables, chapattis and
curd. Chips and snacks packet are
filled with nitrogen gas. If they are filled with oxygen, they will get rancid.
a) What
is meant by rancidity?
b) How
do you preserve butter?
c) Why
chips are packed with nitrogen gas?
24. Three students,
A, B and C were asked to prepare the Lassaigne’s extract independently by
fusing
the compound with
sodium. Then, they added solid ferrous sulphate and dilute sulphuric acid to a part of Lassaigne’s extract. Both A and B got
Prussian blue colour but C got red colour. Can you help them with equations and
reasons? Write the chemical equations to explain the formation of compounds of different colours.
Or
a) What is the principle of
chromatography?
b) How can forgery be detected
with the help of chromatography?
c) Is it possible to separate
components of orange ink by chromatography?
d) Name the stationary and mobile
phase in paper chromatography.
e) What is the suitable adsorbent
in the process of column chromatography?
25. Give reasons:
a) Why silicones are used for
nipples of feeding bottles?
b) Why are silicones used in
cosmetic plants?
c) Why silicones are
water-repellant?
d) Why are silicones thermally
stable?
e) Are silicones safe for
environment?
Or
i) If a salt ‘A’ gives the
following results:
a) Its aqueous solution is
alkaline to litmus. b) On strong heating, ‘A’ swells up to a glassy material
‘B’.
c) When concentrated HCl is added
to a hot solution of ‘A’ white crystals of an acid ‘C’ separates out.
Write the chemical equations for
the reactions and identify ‘A’, ‘B’ and ‘C’.
ii) Complete the equations:
a) 2Al + 6HCl _
b) 8BF3
+
6LiH _
26.
i) What is the change in internal
energy in a process, 701 J of heat is absorbed by a system and 394 J of work is done by the
system.
ii) The equilibrium constant for
the reaction is 10. Calculate the value of ΔGθ. Given R =
8.0
J/mol, T = 300 K.
Or
Calculate the lattice energy for
the change of Li+ (g) + Cl-(g) _ LiCl(s),
Δsub Hθ
of
Li = 160.67 kJ/mol, Δdiss Hθ of Cl2
=
244.34 kJ/mol,
Δle Hθ
of
Li (g) = 520.07 kJ/mol, Δeg Hθ of Cl (g) = -
365.26 kJ/mol,
Δr Hθ
of
LiCl (s) = - 401.66 kJ/mol.
Is the reaction spontaneous or not?
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