ST.

ARNOLD’S CENTRAL SCHOOL, PUNE

FINAL EXAMINATION(2022-23)
SUBJECT - CHEMISTRY
STD: XI __ ______ M.M:70
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 carrying1 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. What is the amount of water produced when 8g of hydrogen is reacted with 32g of oxygen?
(a) 2 mole (b) 1mole
(c) 3 mole (d) 0.5mole

2. The four quantum numbers of the valence electron of potassium are (K atomic no.19)
(a) 4, 1, 1, 1/2 (b) 4, 0, 0, 1/2
(c) 4, 1, 0, 1/2 (d) 4, 4, 0, 1/2

3. Which of the following molecules have trigonal planar geometry?

(a) BF3 (b) NH3
(c) PCl3 (d) IF3

4. An isolated system is a system in which

(a) there is no exchange of energy with the surrounding.
(b) there is exchange of mass and energy with the surrounding.
(c) there is no exchange of energy and mass with the surrounding.
(d) there is no exchange of mass with the surrounding.

5. Le Chatelier’s principle is applicable to:

(a) only homogeneous chemical reversible reactions
(b) only heterogeneous chemical reversible reactions
(c) only physical equilibrium
(d) all systems, chemical or physical in equilibrium.

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6. The I.U.P.A.C. name of CH3COCH(CH3)2 is
(a) 3-methyl-2-butanone (b) Isopropyl methyl ketone
(c) 2-methyl-3-butanone (d) 4-methyl isopropyl ketone

7. A tertiary butyl carbocation is more stable than a secondary butyl carbocation due to which of the
following
(a) –I effect of -CH3 group (b) +R effect of -CH3group
(c) Hyperconjugation (d) -R effect of -CH3 group

8. What acts as electrophile in Sulphonation of benzene?

(a) SO2 (b) SO3H+
(c) SO3 (d) SO3H–

9. The oxidation number of S in NaHSO4—————–

(a) 4 (b) +2
(c) -2 (d) +6

10. Which of the following electron configurations is correct for iron, (atomic number 26)?
(a)[Kr]4s 1 ,3d 6 (b)[Kr]4s 1 ,3d 7
(c)[Ar]4s 2 ,3d 6 (d)[Kr]4s 2 ,3d 6

11. Which of the following is a path function?

(a)Enthalpy (b) Heat
(c) Entropy (d) Gibb’s free energy

12.What is the decreasing order of stability among the following alkenes:

(I) n-butene, (II) cis-2-butene (III) trans-2-butene
(a) III > II > I (b) III > I > II
(c) I > II > III (d) II > I > III

13. Butene-1 may be converted to butane by reaction with

( a) Pd/H2 (b) Zn/HCl
(c) Sn / HCl (d) Zn – Hg

14. Write IUPAC names of the products obtained by the ozonolysis of Pent-2-ene
(a) Product (I) is ethanal and Product (II) is propanal.
(b) Product (I) is ethanal and Product (II) is benzaldehyde
(c) Product (I) is benzaldehyde and Product (II) is propanal.
(d) Product (I) is ethanol and Product (II) is propanol.

For question number 9 and 10, two statements are given – one labeled Assertion (A) and the other
labeled as Reason (R). Select the correct answer to these questions from the codes (a), (b), (c) and (d)
as given below
a. Both A and R are true and R is correct explanation of the assertion.
b. Both A and R are true but R is not correct explanation of the assertion.
c. A is true but R is false.
d. A is false but R is true.

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15. Assertion: Electron gain enthalpy can be exothermic or endothermic.
Reason: Electron gain enthalpy provides a measure of the ease with which an atom adds an
electron to form anion. 1

16. Assertion: The bond order of helium is always zero.

Reason: The number of electrons in bonding molecular orbital and antibonding molecular
orbital is equal. 1

17. Assertion: Pressure is an intensive property.

Reason: Pressure is defined as force by area. The ratio of two extensive properties is an
intensive property. 1

18. Assertion: Chain isomerism is observed in compounds containing four or more than four carbon
atoms.
Reason: Only alkanes show chain isomerism. 1

SECTION-B

This section contains 7 questions with internal choice in two questions. The following questions are
very short types and carry 2 marks each.

19. Draw Newman’s and Sawhorse projections of ethane and label them. 2

20. Derive the structure of the following compounds from their IUPAC names?
(a)Hexa-1, 3-dien-5-yne (b) 5-Oxohexanoic acid.
OR
Write the IUPAC names of the following compounds from their given structures.

(a) (b) 2

21. Write the main products when

(i) Alkynes are heated with mercuric sulphate and dilute sulphuric acid at 333 K.
(ii) Hydrogen halides (HCl, HBr, HI) added to alkynes.
OR
How would you convert the following?
(i) Sodium salt of benzoic acid to benzene.
(ii) Arenes to Haloarenes. 2

22. (i)What is buffer solution?

(ii)Why does pH of blood not change despite of variety of food and spices we eat? 2

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23. (i)Define enthalpy of fusion.
(ii) Is the enthalpy of neutrilisation of HCl is same as that of H 2SO4? Justify your answer. 2

24. Define hydrogen bond. Why do compounds having hydrogen bonding have high melting and boiling
points? 2

25. Explain the trends in following physical properties while moving across the period in a periodic table.
i. Electron gain Enthalpy ii. Electronegativity 2

SECTION-C

This section contains 5 questions with internal choice in two questions. The following questions are short
types and carry 3 marks each.

26. Give answers by pairing with correct statement:

(i) Hund’s Rule (a) determines the size and to large extent the
energy of the orbital.
(ii) Aufbau Principle (b)No two electrons in an atom can have the
same set of four quantum numbers
(iii) Pauli Exclusion Principle (c) pairing of electrons in the orbitals
belonging to the same subshell does not take
place until each orbital belonging to that
subshell has got one electron each.
(iv) Effective nuclear charge (d) In the ground state of atoms, orbitals are
filled in the order of their increasing energies.
(v) Principal quantum number (e)The attractive positive charge of nuclear
protons acting on valence electrons depends on
no.of protons and electrons in a polyelectronic
atom.
(vi) Magnetic quantum number (f) it is impossible to measure or calculate
exactly, both the position and the momentum
of an object.
(g) gives information about the spatial
orientation of the orbital with respect to
standard set of co-ordinate axis.
3
27. (i) If 10 volumes of dihydrogen gas react with five volumes of dioxygen gas, how many volumes
of water vapour would be produced?
2H 2 +O 2 → 2H 2 O(g)

(ii) How many moles of methane are required to produce 22g of CO2 (g) after combustion?
CH4 (g) + 2O2 (g) → CO2 (g) + 2H2O (g) 3

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28. Dinitrogen and dihydrogen react with each other to produce ammonia according to the
following chemical equation:
N 2 (g) + 3H 2 (g)2NH 3 (g)
(i) Calculate the mass of ammonia produced if 2 x 103 g N2 reacts with 1 x 103 g of H2.
(ii) Will any of the two reactants remain unreacted?
(iii) If yes, which one and what would be its mass? 3

29. Write the reactions showing preparation of alkenes from

(i) Alkyl halides (ii) Vicinal dihalides (iii) Alcohols 3

30. (i) Justify that the reaction: 2Cu 2 O(s) + Cu 2 S( s) → 6Cu(s) + SO 2 (g) is a redox reaction.
(ii) Balance the following redox reactions by ion electron method.
MnO 4 – (aq) + I – (aq) → MnO 2 (s) + I 2 (s) (in basic medium)

OR

(i) Calculate the oxidation number of Sulphur and Nitrogen in

a. S 2 O 3 2 − b.NO 3 -
(ii) Balance the following equation by half reaction method) (in acidic medium).
Fe 2 + ( aq) + Cr 2 O 7 2 – (aq) → Fe 3 + (aq) + Cr 3 + ( aq) 3

SECTION-D

The following questions are case-based questions and carries 4 (1+1+2) marks each. Read the
passage carefully and answer the questions that follow.

31. When a liquid evaporates in a closed container, molecules with relatively higher kinetic energy escape
the liquid surface into the vapour phase and number of liquid molecules from the vapour phase strike
the liquid surface and are retained in the liquid phase. It gives rise to a constant vapour pressure because
of an equilibrium in which the number of molecules leaving the liquid equals the number returning to
liquid from the vapour. We say that the system has reached equilibrium state at this stage.
At equilibrium, the rate of evaporation is equal to the rate of condensation. It may be represented by
H 2 O ( l ) ⇌ H 2 O (g)
The mixture of reactants and products in the equilibrium state is called an equilibrium mixture.
Equilibrium can be established for both physical processes and chemical reactions. When the reactants in
a closed vessel at a particular temperature react to give products, the concentrations of the reactants keep
on decreasing, while those of products keep on increasing for some time after which there is no change
in the concentrations of either of the reactants or products. This stage of the system is the dynamic
equilibrium. It is seen that acid (or base) dissociation equilibrium is dynamic involving a transfer of
proton in forward and reverse directions. The concept of conjugate acid-base pair is related to Bronsted-
Lowry acid-base theory and according to this theory, acid is a proton donor while base is a proton
acceptor.

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 (a) The ionisation of hydrochloric in water is given below:
HCI(aq) + H2O (l) →H3O+ (aq) + CI– (aq)
Label two conjugate acid-base pairs in this ionisation. 1

(b) In a given acidic buffer solution (CH3COOH +CH3COONa). Which ionic species are mainly
present in the solution? 1

(c) On basis of Le-Chatelier’s principle explain how can the temperature and pressure be adjusted to
increase the yield of ammonia in the following reaction.
N2(g)+3H2(g) → 2NH3(g), ΔH= −92.38 kJ mol−1
OR
PCl5, PCl3 and Cl2 are at equilibrium at 500K in a closed container and their concentrations are
0.8 × 10–3 mol L–1, 1.2 × 10–3 mol L–1 and 1.2 × 10–3 mol L–1 respectively.
The value of Kc for the reaction PCl3 (g) + Cl2 (g) → PCl5 (g) 2

32. Molecular orbitals are formed by the overlap of atomic orbitals. Two atomic orbitals combine to form
two molecular orbitals called bonding molecular orbital (BMO) and anti bonding molecular orbital
(ABMO). Energy of anti-bonding orbital is raised above the parent atomic orbitals that have combined
and the energy of the bonding orbital is lowered than the parent atomic orbitals.
Different atomic orbitals of one atom combine with those atomic orbitals of the second atom which
have comparable energies and proper orientation. Further, if the overlapping is head on, the molecular
orbital is called ‘Sigma’, (σ) and if the overlap is lateral, the molecular orbital is called ‘pi’, (π).
The molecular orbitals are filled with electrons according to the same rules as followed for filling
of atomic orbitals. However, the order for filling is not the same for all molecules or their ions.
Bond order is one of the most important parameters to compare the strength of bonds.

(a) Which bond is more polar in the following pairs of molecules?

(i) H3C−H and H3C−Br (ii) H3C−NH2 and H3C−OH 1
(b) Describe the hybridisation in case of BCl3 1
(c) What is the total number of sigma and pi bonds in the following molecules?
(i) C2H2 (ii) C2H4

OR

Draw molecular orbital diagram for Cl2 molecule and calculate its bond order. 2

SECTION-E
The following questions are long answer type and carry 5 marks each. Two questions have an
internal choice.

33. (a) Explain the following with one example in each case of covalent bonds.
(i) Homolytic fission (ii) Heterolytic fission 2
(b) What are nucleophiles? Give 2 example of nucleophiles. . 2
(c) What are the necessary conditions for any system to be aromatic? 1
OR

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 (a) What is homologous series? Write first four homologous of alcohols and give their IUPAC names. 2
(b) Explain the following isomerism by giving one example in each case.
(i) Position isomerism (ii) Functional isomerism 2
(c) Show the electron shift for C6H5OH molecule using curved arrow notation. 1

34. (a) Calculate the enthalpy change for the reaction H2 + Br2 → 2HBr
The bond enthalpies of H-H, Br-Br and H-Br are 435 kJ mol-1, 192 kJ mol-1
and 364 kJ mol-1 respectively. 2
(b) What do you mean by thermodynamics state functions? Give two examples. 2
(c) State Hess’s Law of Constant Heat Summation. 1
OR

(a) Define specific heat capacity and molar heat capacity. 2

(b) Write mathematical equations of first law of thermodynamics for the following processes
(i) Adiabatic process (ii) Isochoric process 1
(c) Calculate the ΔH of the following reaction:
CO2 (g) + H2O (g) → H2CO3 (g)
If the standard values of ΔHf are
CO2 (g): -393.509 KJ /mol
H2O (g): -241.83 KJ/mol
H2CO3(g): -275.2 KJ/mol 2

35. (a) Why the energy of 2s orbital of hydrogen atom is greater than that of 2s orbital of lithium? 1
(b) Write the electronic configurations of the following ions:
(i) Ca +2 (ii) O2– 1
(c) Identify the iso-electronic ions from the following pairs?
(i) Na+ and Mg2+ (ii) Al3+and O2- 1
(d) What are the atomic numbers of elements whose outermost electrons are represented by
(i) 2p3 (ii) 3p5 1
(e) How many electrons will be present in the sub-shells having ms value of –1 for n = 4 ? 1

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