zwitter ion

burnpur

Academic Session 2025-2026

Roll No........................ zwitter ion(setA) Date........................

HalfHalf yearly
yearly exam
exam
Total Time: 3 Hrs 00 Mins Max Marks: 70

General Instructions
Read the following instructions carefully.
(a) There are 33 questions in this question paper with internal choice.
(b) SECTION A consists of 16 multiple -choice questions carrying 1 mark each.
(c) SECTION B consists of 5 short answer questions carrying 2 marks each.
(d) SECTION C consists of 7 short answer questions carrying 3 marks each.
(e) SECTION D consists of 3 long answer questions carrying 5 marks each.
(f) SECTION E consists of 2 case - based questions carrying 4 marks each.
(g) All questions are compulsory.
(h) Use of log tables and calculators is not allowed.

Standard/Class:
Class: xii xii Subject: CHEMISTRY

Section A

Objective(MCQ) - (1 Marks)
1. Considering the formation, breaking and strength of hydrogen bond, predict [1]
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.

2. Maximum amount of a solid solute that can be dissolved in a specified [1]

amount of a given liquid solvent does not depend upon __________.
(i) Temperature (ii) Nature of solute
(iii) Pressure (iv) Nature of solvent

3. We have three aqueous solutions of NaCl labelled as ‘A’, ‘B’ and ‘C’ with [1]
concentrations 0.1M, 0.01M and 0.001M, respectively. The value of van’t
Hoff factor for these solutions will be in the order .
(i) iA < iB < iC
(ii) iA > iB > iC
(iii) iA = iB = iC
(iv) iA < iB > iC
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4. The Standard electrode potentials for the half cell reactions are as follows [1]
Zn ? Zn2+ + 2e– [E° = 0.41 V]
Fe ? Fe2+ + 2e– [E° = 0.76 V]
(a) -0.35 V (b) 0.35 V
(c) + 1.17 V (d) -1.17 V
5. How many coulombs are required for the oxidation of 1 mole of H2O to O2? [1]

(a) 1.93 × 105 C (b) 9.65 × 104 C

(c) 3.86 × 105 C (d) 4.825 × 105 C

6. Standard solution of KNO3 is used to make a salt bridge because [1]

(a) Velocity of K+ is greater than that of NO−3.
(b) Velocity of NO−3 is greater than that of K+.
(c) Velocity of both K+ and NO−3 are nearly same
(d) KNO3 is highly soluble in water.

7. The unit of rate and rate constant are same for a [1]
(a) zero order reaction (b) first order reaction
(c) second order reaction (d) third order reaction
8. For a reaction x –> y the rate of reaction becomes twenty seven times when [1]
the concentration of X is increased three times. What is the order of the
reaction?
(a) 2 (b) 1 (c) 3 (d) 0
9. Which of the following compounds will have highest melting point? [1]
(a) Chlorobenzene (b) o-Dichlorobenzene
(c) m-Dichlorobenzene (d) p-Dichlorobenzene
10. Butane nitrile can be prepard by heating. [1]
(a) propyl alcohol with KCN (b) butyl chloride with KCN
(c) butyl alcohol with KCN (d) propyl chloride with KCN
11. A compound X with the molecular formula C2H8O can be oxidised to [1]
another compound Y whose molecular formulae is C3H6O2. The compound
X may be
(a) CH3CH2OCH3 (b) CH3CH2CHO
(c) CH3CH2CH2OH (d) CH3CHOHCH3

12. Phenol when treated with excess of bromine water gives a white precipitate [1]
of
(a) 2, 4, 6-tribromophenol (b) o-bromophenol
(c) p-bromophenol (d) bromobenzene
13. Assertion (A): The Daniell cell becomes dead after some time. [1]
Reason (R): Oxidation potential of zinc anode decreases and that of copper
increases.
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 a) Both A and R are correct and R is the correct explanation of A.
b) Both A and R are correct but R is not the correct explanation of A.
c) A is true but R is false. d) A is false but R is true.
14. Assertion (A): All collisions of reactant molecules lead to product formation. [1]
Reason (R): Only those collisions in which molecules have correct orientation
and sufficient kinetic energy lead to the compound formation.
a) Both A and R are correct and R is the correct explanation of A.
b) Both A and R are correct but R is not the correct explanation of A.
c) A is true but R is false. d) A is false but R is true.
15. Assertion (A): Vinyl halides do not give nucleophilic substitution reaction. [1]
Reason (R): Vinyl group is electron donating in vinyl halides.
a) Both A and R are correct and R is the correct explanation of A.
b) Both A and R are correct but R is not the correct explanation of A.
c) A is true but R is false. d) A is false but R is true.
16. Assertion (A): Phenol undergoes Kolbe's reaction but ethanol does not. [1]
Reason (R): Phenol is more acidic than ethanol.
a) Both A and R are correct and R is the correct explanation of A.
b) Both A and R are correct but R is not the correct explanation of A.
c) A is true but R is false. d) A is false but R is true.

Section B

Subjective - (2 Marks)
17. Which of the following solutions has higher freezing point? [2]
0.05 M Al2(SO4)3, 0.1 M K3[Fe(CN)6] Justify.

18. Discuss biological and industrial importance of osmosis. [2]

19. The vapour pressures of pure liquids A and B are 450 mm and 700 mm of Hg [2]
respectively at 350 K. Calculate the composition of liquid mixture if total
vapour pressure is 600 mm of Hg. Also find the composition of the mixture
in vapour phase.

OR
A solution 0.1 M of Na2SO4 is dissolved to the extent of 95%. What would be

its osmotic pressure at 27°C? (R = 0.0821 L atm K-1 mol-1)

20. Derive integrated rate equation for rate constant of a first order reaction. [2]
21. tert-Butylbromide reacts with aq. NaOH by SN1 mechanism while n-butyl [2]
bromide reacts by an SN2 mechanism. Why?

Section C
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 Subjective - (3 Marks)
22. (i) Define the following terms: [3]
(a) Mole fraction (b) van’t Hoff factor
(ii) 100 mg of a protein is dissolved in enough water to make 10.0 mL of a
solution. If this solution has an osmotic pressure of 13.3 mm Hg at 25°C,
what is the molar mass of protein? (R = 0.0821 L atm. mol-1 K-1 and 760 mm
Hg = 1 atm.)
23. What type of battery is lead storage battery? Write the anode and the [3]
cathode reactions and the overall reaction occurring in a lead storage
battery.
24. E°cell for the given redox reaction is 2.71 V. [3]

Mg(s) + Cu2+(0.01 M) → Mg2+(0.001 M) + Cu(s)

Calculate Ecell for the reaction. Write the direction of flow of current when an
external opposite potential applied is
(i) less than 2.71 V and (ii) greater than 2.71 V
25. The rates of most reactions double when their temperature is raised from [3]
298 K to 308 K. Calculate their activation energy. [R = 8.314 JK-1 mol-1]
26. (i) State one use each of DDT and iodoform. [3]
(ii) Which compound in the following couples will react faster in SN2
displacement and why?
(a) I -Bromopentane or 2-bromopentane
(b) I-Bromo-2-methyl butane or 2-Bromo-2-methyl butane
27. How will you convert [3]
(i) Propan-2-ol to 2-methylpropan-2-ol
(ii) Aniline to phenol
(iii) Ethanol to propane nitrile
(iv) Phenol to toluene
(v) Formaldehyde to ethanol?
28. Name the following compounds according to IUPAC system. [3]

OR
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 Give structures of the products you would expect when each of the following
alcohol reacts with (a) HCl-ZnCl2 (b) HBr and (c) SOCl2 .
(i) Butan-1-ol
(ii) 2-Methylbutan-2-ol

Section D

Subjective - (5 Marks)
29. (a) The decomposition of A into products has a value of K as 4.5 × 103 s-1 at [5]
10°C and energy of activation 60 kj mol-1. At what temperature would K be
1.5 × 104 s-1?
(b) (i) If half life period of a first order reaction is x and 3/4,th life period of
the same reaction is y, how are x and y related to each other?
(ii) In some cases it is found that a large number of colliding molecules have
energy more than threshold energy, yet the reaction is slow. Why?

OR
For the hydrolysis of methyl acetate in aqueous solution, the following
results were obtained:

t/s 0 10 20

[CH3COOCH3]/mol L-1 0.10 0.05 0.025

(i) Show that it follows pseudo first order reaction, as the concentration of
water remains constant.
(ii) Calculate the average rate of reaction between the time interval 10 to 20
seconds. (Given : log 2 = 0.3010, log 4 = 0.6021)
30. (i) Identify the chiral molecule in the following pair: [5]

(ii) Write the structure of the product when chlorobenzene is treated with
methyl chloride in the presence of sodium metal and dry ether.
(iii) Write the structure of the alkene formed by dehydrohalogenation of 1-
Bromo-1- methylcyclohexane with alcoholic KOH.

OR
Draw the structures of major monohalo products in each of the following
reactions:

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31. (a) The e.m.f. of the following cell at 298 K is 0.1745 V: [5]
Fe (s) | Fe2+ (0.1 M) | | H+ (x M) | H2 (g) (1 bar) | Pt (s)
Given: E°Fe2+Fe = – 0.44 V

Calculate the H+ ions concentration of the solution at the electrode where

hydrogen is being produced.
(b) Aqueous solutions of copper sulphate and silver nitrate are electrolysed
by 1 ampere current for 10 minutes in separate electrolytic cells. Will the
mass of copper and silver deposited on the cathode be same or different?
Explain your answer.

OR
(i) Following reactions occur at cathode during the electrolysis of aqueous
sodium chloride solution:
Na+(aq) + e– → Na(s) E° = -2.71V
H+(aq) + e– → H2(g) E ° = 0.00 V
On the basis of their standard reduction electrode potential (E°) values,
which reaction is feasible at the cathode and why?
(ii) Why does the cell potential of mercury cell remain constant throughout
its life?

Case-Study

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32. [4]

33. [4]

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