TERM
1 (2022-23) CLASS XII
CHEMISTRY
THEORY (043)
MM:70
Time: 3 hours
General
Instructions: Read the following instructions carefully.
a) There are
35 questions in this question paper with internal choice.
b) SECTION A
consists of 18 multiple-choice questions carrying 1 mark each.
c) SECTION B consists of 7 very short answer
questions carrying 2 marks each.
d) SECTION C
consists of 5 short answer questions carrying 3 marks each.
e) SECTION D consists of 2 case- based
questions carrying 4 marks each.
f) SECTION E
consists of 3 long answer questions carrying 5 marks each.
g) All
questions are compulsory.
h) Use of
log tables and calculators is not allowed.
SECTION A
The following questions are multiple-choice questions with one correct answer. Each question carries 1 mark. There is no internal choice in this section.
1. When1 mole of CrCl3.6H2O
is treated with excess of AgNO3, 3 moles of AgCl are obtained. The
formula of the complex is
a)
[CrCl3(H2O)3].3H2O
b)
[CrCl2(H2O)4].2H2O
c)
[CrCl(H2O)5Cl2.H2O
d)
[Cr(H2O)6].Cl3
2.
Which
of the following alkyl halides will undergo SN1 reaction most
readily?
a)
(CH3)3C-F b) (CH3)3C-I c) (CH3)3-Br d) (CH3)3C-Cl
3.
IUPAC
name of the compound CH3- CH- OCH3
|
CH3
a)
1-methoxy-1-methyl-methylethane
b)
2-methoxy-2-methylethane
c)
2-methoxypropane
d)
Isopropylmethylether
4.
Lucasreagent
produces cloudiness immediately with
CH3
|
a) CH3 -C- CH3
|
OH
b)
CH3 - CH-
CH2 -CH3
|
OH
c)
CH3 - CH2- CH2 - OH
d)
CH3 - CH-
CH2 – OH
|
CH3
5.
Which
of the following azeotropic solutions of two liquids has the boiling point less
than the boiling point of its constituents molecules?
a)
CHCl3
& CH3COCH3
b)
CS2&
CH3COCH3
c)
CH3CH2OH
& CH3COCH3
d)
CH3CHO
& CS2
6.
The
osmotic pressure of solution increases if
a)
The
volume of the solution increased.
b)
The
number of solute molecules is increased.
c)
Temperature
is decreased.
d)
Solution
constant is increased.
7.
Using
the given data find out strongest reducing agent.
E0Cr2O72-/Cr
= 1.33V E0Cl2/Cl-
= 1.36V
E0MnO4-/Mn2+= 1.51V
E0Cr3+/Cr= -0.74V
a) Cl-
b) Cr
c) Cr3+
d) Mn2+
8. An electrochemical cell can behave like electrolytic cell when---
a)
Ecell
= 0
b)
Ecell>
E ext
c)
Ecell<
E ext
d) Ecell = E ext
9. Which of the following is the reason for zinc not exhibiting variable oxidation state?
a)
Inert
pair effect
b)
Completely
filled 3d subshell
c)
Completely
filled 4s- subshell
d) Common ion effect
10. Rate law for the reaction A + 2B → C is found to be
Concentration of reactant ‘B’ is doubled, keeping the concentration of ‘A’ constant, the value of rate constant will be….
a) The same b) doubled c) halved d) quadrupled
11. Which of the following statements about [Co(CN)6]3- is true
a) [Co(CN)6]3- has no unpaired electrons & will be in low spin configuration.
b) [Co(CN)6]3- has four unpaired electrons & will be in low spin configuration.
c) [Co(CN)6]3- has four unpaired electrons & will be in high spin configuration.
d) [Co(CN)6]3- has no unpaired electrons & will be in high spin configuration.
12. Identify A, B, C & D
D
↑KCN
AgCN Alc KOH
C←C2H5Cl → A
↓Aq. KOH
B
a)
A
= C2H4,B=C2H5OH,C=C2H5NC,D=
C2H5CN
b)
A
= C2H5OH,B=C2H4,C=C2H5CN,D=
C2H5CN
c)
A
= C2H4,B=C2H5OH,C=C2H5CN,D=
C2H5NC
d)
A
= C2H5OH,B=C2H4,C=C2H5NC,D=
C2H5CN
13. The boiling point of alcohols are
higher than those of hydrocarbons of comparable masses due to
a)
Hydrogen
bonding
b)
Ion-dipole
c)
Dipole-dipole
interaction
d)
Van
der Waal’s force
14. Consider the following plot between
lnk and 1/T,
↑
1/T
In this plot, the intercept &
slope respectively are
a)
-Ea/R
: ln A b) ln A :
-Ea/R c) Ea/R
: -lnA d) Ea/R: A
For the question number 15 to 18, two
statements are given- one labelled Assertion &the other labelled as
Reason(R). Select the correct answer to these questions from codes (a), (b),
(c) & (d) as given below:
a. Both A and R are true and R is the correct explanation
of A
b. Both A and R are true but R is not the correct
explanation of A.
d. A is false but R is true.
15. Assertion (A) : Aquatic species are more comfortable
in cold water than in warm water.
Reason (R): Different
gases have different KH values at the same temperature.
16. Assertion (A) :Zn, Cd & Hg cannot be regarded as
transition elements.
Reason(R): These elements do not belong to d-
block of the periodic table.
17. Assertion (A) :Tetrahedral complexes do not show
geometrical isomerism.
Reason (R) :The relative position of the
unidentate ligands attached to the central atom are the same with respect to
each other.
18. Assertion (A) :The inversion of cane sugar
H+
C12H22O11
+ H2O→
C6H12O6 + C6H12O6 is a Pseudo first order reaction.
Reason (R) :H2Oin this reaction is
present in very less amount as compared to C6H12O6.
SECTION B
This section
contains 7 questions with internal choice in two questions. The following
questions are very short answer type and carry 2 marks each.
19. Arrange each set of following
compounds in order of increasing boiling points.
(i)
Bromomethane,
Bromoform, Chloromethane, dibromo methane.
(ii)
1-
chloropropane, isopropyl chloride, 1- chlorobutane.
20. A first order reaction has a rate
constant 1.15x10-3s-1. How long will 5g of this reactant
take to reduce to 3g?
(Given: log 5 =0.6990,
log 3 = 0.4771)
21. Write the mechanism of acid
dehydration of ethanol to yield ethene.
Or H+
Explain the mechanism of
following reaction: CH3-CH2-OH
→ CH2=CH2 + H2O
22. The conversion of molecule X to Y follows second order kinetics. If
concentration of X is increased to three times, how will it affect the rate of
formation of Y.
23. Explain [Co(NH3)6]3+
is an inner orbital complex whereas [Ni(NH3)6]2+
is an outer orbital complex.
Or
Ni(H2O)6]2+
is green in colour whereas [Ni(H2O)4(en)]2+ is
blue in colour, give reason in support of your answer.
24. From the given cells: lead storage
cell, mercury cell, Fuel cell & dry cell
Answer the following
questions
I)
Which
cell is used in hearing aids?
II)
Which
cell was used in Apollo Space programme
III)
Which
cell is used in automobiles & inverters
IV)
Which
cell does not have a long life.
25. In a coordination entity, the
electronic configuration of the metal ion is t2g2eg1.
i)
Is
the coordination compound a high spin or low spin complex.
ii)
Draw
the crystal field splitting diagram for the above complex.
SECTION C
This section
contains 5 questions with internal choice in two questions. The following
questions are short answer type and carry 3 marks each.
26. State Henry’s law. Write its two
applications. What is effect of temperature on the solubility of gas in liquid.
Or
State the Raoult’s Law
for a solution containing non volatile solute. What type of deviation shown by
a solution of chloroform & acetone & why?
27. Give reasons for any 3:
i) The
enthalpies of atomisation of transition metals are high.
ii) The
transition metals generally form coloured compounds
iii) Transition
metals & their many compounds acts as good catalyst.
iv) The
transition metals & many of their compounds show paramagnetic behaviour.
28. Write the Nernst equation& emf of
the following cell at 298K.
Mg(s) |Mg2+ (0.001M)
|| Cu2+(0.0001M)| Cu(s)
Given that, E0Mg2+/Mg = -2.36V
& E0 Cu2+/Cu =
0.34V (log 10 = 1)
29. For the complex [NiCl4]2-,
write
i) The IUPAC name
ii) The
hybridisation
iii) Shape of complex
30. For a certain chemical reaction variation in the concentration ln [R] vs time plot given For this reaction
I) What is order of reaction.
II) What are units of rate constant k?
III) Give the relation between k & t1/2( half life period) ln[R]
↑
SECTION D
The following questions
are case-based questions and carries 4 marks . Read the passage carefully and
answer the questions that follow.
31. Williamson synthesis is one of the
best method for the preparation of ethers. It involves the treatment of alkyl
halide with a suitable sodium alkoxide. Williamson’s synthesis involves
nucleophilic substitution of the halogen atom of alkyl halide by an alkoxide group
as shown
R-ONa
+ R’X → R-O-R’ + NaX
When alkyl halide used in
the reaction is primary, Willamson’s synthesis proceed via SN2
mechanism leading to the preparation of an ether. This method is a versatile
method for the synthesis of both symmetrical & unsymmetrical ethers.
i)
Why
is Williamson’s synthesis not applicable when the alkyl halide used is
tertiary.
ii)
Write
the chemical equation for preparation of (CH3)3C-O-C2H5(tert-butyl
ethyl ether) by using alkyl halide & sodium alkoxide .
iii)
(CH3)3C-
O-CH3 + HI
→ A + B
Write the structure& IUPAC name of A & B.
Or
What happen when ethyl phenyl ether react with
HI? Write chemical equation.
32. Students are often fascinated by extreme sports
such as SCUBA( Self-contained underwater breathing Apparatus) diving. But scuba divers must be very conscious of
Caisson’s disease, commonly called ‘ The Bends’. This condition is related more
to Henry’s Law, which states that more gas will be dissolved in a liquid when
the gas is pressurized. Because of the water pressure, body tissue absorbs
nitrogen gas faster as a driver descends than when ascending to the surface.
However, if a driver ascends too quickly, nitrogen gas bubbles will form in
body tissue rather than being exhaled. These nitrogen bubbles cause severe
pain.
i)
A condition that
is related to nitrogen solubility at high pressure is:
a) Anoxia b)
Bends
b) Nausea d)
None of the above
ii)
Bends are caused
due to:
a) Blockage of blood capillaries by N2bubbles.
b) Blockage of blood capillaries by O2bubbles.
c) Blockage of blood capillaries by H2bubbles.
d) Blockage of blood capillaries by CO2bubbles.
iii)
Scuba divers must
use air diluted with:
a) Hydrogen
b) Helium
c) Neon
d) Nitrogen
iv)
Henry’s law is
applicable only when:
a) The pressure of gas is not too high and
temperature is not too low.
b) The gas should not undergo any chemical
change.
c) The gas should not undergo association or
dissociation in the solution.
d) All of
these conditions are applicable.
SECTION E
The following
questions are long answer type and carry 5 marks each. Two questions have an
internal choice.
33. When chromite ore FeCr2O4
is fused with NaOH in the presence of air, a yellow-coloured compound (A) is
obtained which on acidification with dilute sulphuric acid gives a compound(B).
Compound (B) on a reaction with KCl forms a orange coloured crystalline
compound (C).
a)
Identify the
compound A,B& C& write the chemical reactionsinvolved.
b)
Complete the
chemical equation
i)
Cr2O72-
+ 6 Fe2+ + 14 H+ →
ii)
2MnO4-
+ 5 C2O42- + 16 H+→
Or
I)
What is
Lanthanoid contraction? What are consequences of Lanthanoid contraction?Name an
important alloy which contains some of lanthanoid metals.
II)
Why is highest
oxidation state of metal exhibited by its oxide & fluoride only.
b) The conductivity of 0.20M solution of KCl at 298K is 0.0248Scm-1. Calculate its molar conductivity.
Or
a) How much charge is required for the reduction of 1 mol of Al3+ to Al.
b) Depict the galvanic cell in which the reaction
Zn(s) + 2 Ag+ → Zn2+ + 2 Ag(s) takes place . Further show:
i) Which of the electrode is negatively charged.
ii) The carrier of the current in the cell.
iii) Individual reaction at each electrode.
35. a) Haloarenes are less reactive than haloalkanes towards nucleophilic substitution reaction. Give reason.
b) Write the chemical equations for i) Swart reaction ii) Wurtz -Fittig reaction
c) Why is solubility of haloalkanes in water very low?
d) Out of SN1 & SN2, which reaction occurs with i) Inversion of configuration ii) racemisation.
ALL THE BEST
