Term 1 Model Examination 2021-22 Chemistry (043) : General Instructions
Term 1 Model Examination 2021-22 Chemistry (043) : General Instructions
Term 1 Model Examination 2021-22 Chemistry (043) : General Instructions
Chemistry (043)
Class : XII Time: 90 Minutes
Max. Marks: 35 11-10-21
General Instructions:
1. The Question Paper contains three sections.
2. Section A has 25 questions. Attempt any 20 questions.
3. Section B has 24 questions. Attempt any 20 questions.
4. Section C has 6 questions. Attempt any 5 questions.
5. All questions carry equal marks.
6. There is no negative marking.
SECTION A
This section consists of 25 multiple choice questions with overall choice to
attempt any 20 questions. In case more than desirable number of questions
are attempted, ONLY first 20 will be considered for evaluation.
1. Which of the following statements is not true about the hexagonal close
packing:
(a) The coordination number is 12.
(b) It has 74% packing efficiency.
(c) Tetrahedral voids of second layer are covered by spheres of third
layer.
(d) In this arrangement, spheres of the fourth layer are exactly aligned
with those of the first layer.
2. Which of the following is true about the value of refractive index of
quartz glass?
(a) Same in all directions
(b) Different in different directions
(c) Cannot be measured
(d) Always zero
3. Iodine molecules are held in the crystals lattice by ________.
(a) London forces
(b) Dipole-dipole interactions
(c) Covalent bonds
(d) Coulombic forces
4. Which of the following defects decrease the density?
(i) Interstitial defect
(ii) Vacancy defect
(iii) Frankel defect
(iv) Schottky defect
(a) (i) , (ii) and (iii)
(b) (ii) and (iii)
(c) (i) and (iii)
(d) (ii) and (iv)
5. Low concentration of oxygen in the blood and tissues of people living
at high altitude is due to _____________.
(i) low temperature
(ii) low atmospheric pressure
(iii) high atmospheric pressure
(iv) both low temperature and high atmospheric pressure
6. Considering the formation, breaking and strength of hydrogen bond,
predict which of the following mixtures will show a positive
deviation from Raoult’s law?
(i) Methanol and acetone.
(ii) Chloroform and acetone.
(iii) Nitric acid and water.
(iv) Phenol and aniline.
7. The number of moles of NaCl in 3 litres of 3M solution is :
(a) 1
(b) 3
(c) 9
(d) 27
(a) a and d
(b) a and b
(c) b and c
(d) c and d
20.The major product obtained on interaction of phenol with NaOH and
CHCl3 is
(a) Benzoic acid
(b) Salicylaldehyde
(c ) Salicylic acid
(d)Aspirin
21. CH3 CH2OH can be converted into CH3CHO by ------------------.
(a) catalytic hydrogenation
(b) treatment with LiAlH4
(c )Treatment with PCC
(d)Treatment with KMnO4
22. Which of the following is not an essential amino acid?
(a) Leucine
(b) Valine
(c )Alanine
(d)Isoleucine
23. Which of the following base is present in DNA but not in RNA?
(a) Adenine
(b) Thymine
(c )Guanine
(d)Cytosine
24. Which one is the complementary base of Adenine in one strand to that in
other strand of DNA?
(a) Guanine
(b)Cytosine
(c )Thymine
(d)Uracil
25. Which one given below is a non-reducing sugar?
(a) glucose
(b)Sucrose
(c )Fructose
(d)Sucrose
SECTION B
This section consists of 24 multiple choice questions with overall choice
to attempt any 20 questions. In case more than desirable number of
questions are attempted, ONLY first 20 will be considered for evaluation.
26. The total number of tetrahedral voids in the face centred unit cell is
________.
(a) 6
(b) 8
(c) 10
(d) 12
27. In a tetragonal crystal system
(a) a=b=c , α=β =90o ≠ɣ
(b) ) a=b≠c , α=β= ɣ =90o
(c) ) a≠b≠c , α=β= ɣ =90o
(d) ) a=b≠c , α=β =90o , ɣ=120o
28. In a solid lattice, the cation has left a lattice site and is located at an
interstitial position. The crystal defect is:
(a) metal excess defect
(b) metal deficiency defect
(c ) Frenkel defect
(d)Schottky defect
Given below are two statements labelled as Assertion (A) and Reason (R)
followed by four options (a), (b), (c) and (d). Select the most appropriate
answer from the options given :
Read the passage given below and answer the following questions(53-55):
Nucleophilic substitution reaction of haloalkane can be conducted according
to both SN 1 and SN 2 mechanisms. However, which mechanism it is based on is
related to such factors as the structure of haloalkane, and properties of leaving
group, nucleophilic reagent and solvent.
Influences of halogen :
No matter which mechanism the nucleophilic substitution reaction is based on,
the leaving group always leave the central carbon atom with electron pair. This
is just the opposite of the situation that nucleophilic reagent attacks the
central carbon atom with electron pair. Therefore, the weaker the alkalinity of
leaving group is , the more stable the anion formed is and it will be more easier
for the leaving group to leave the central carbon atom; that is to say, the
reactant is more easier to be substituted. The alkalinity order of halogen ion is
I− < Br− < Cl− < F− and the order of their leaving tendency should be I− > Br− > Cl−
> F− . Therefore, in four halides with the same alkyl and different halogens, the
order of substitution reaction rate is RI> RBr > RCl > RF . In addition, if the
leaving group is very easy to leave, many carbocation intermediates are
generated in the reaction and the reaction is based on SN 1 mechanism. If the
leaving group is not easy to leave, the reaction is based on SN 2 mechanism.
Influences of solvent polarity:
In SN 1 reaction, the polarity of the system increases from the reactant to the
transition state, because polar solvent has a greater stabilizing effect on the
transition state than the reactant, thereby reduce activation energy and
accelerate the reaction. In SN 2 reaction, the polarity of the system generally
does not change from the reactant to the transition state and only charge
dispersion occurs. At this time, polar solvent has a great stabilizing effect on Nu
than the transition state, thereby increasing activation energy and slow down
the reaction rate. For example, the decomposition rate ( SN 1 ) of tertiary
chlorobutane in 25℃ water (dielectric constant 79) is 300000 times faster than
in ethanol (dielectric constant 24). The reaction rate (SN 2 ) of 2-bromopropane
and NaOH in ethanol containing 40% water is twice slower than in absolute
ethanol. In a word, the level of solvent polarity has influence on both SN 1 and
SN 2 reactions, but with different results. Generally speaking, weak polar
solvent is favourable for SN 2 reaction, while strong polar solvent is favourable
for SN 1 reaction, because only under the action of polar solvent can
halogenated hydrocarbon dissociate into carbocation and halogen ion and
solvents with a strong polarity is favourable for solvation of carbocation,
increasing its stability. Generally speaking, the substitution reaction of tertiary
haloalkane is based on SN 1 mechanism in solvents with a strong polarity (for
example, ethanol containing water).
(Ding, Y. (2013). A Brief Discussion on Nucleophilic Substitution Reaction on
Saturated Carbon Atom. In Applied Mechanics and Materials (Vol. 312, pp.
433-437). Trans Tech Publications Ltd.)