Class 11 Question Paper 2023-24 Chemistry (Half Yearly)

2023-24
HALF YEARLY
EXAM
NCERT BASED
SYLLABUS
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FOR
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Half Yearly Exam 2023-24
Question Paper

Class - XI Subject – Chemistry
Time – 3 Hours Maximum 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 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 calculators is not allowed.

SECTION A
1. The number of atoms present in 16 g of oxygen is:
a) 6.02x1011. 5 b) 3.01x1023 c) 3.01 x1011. 5 d) 6.02 x 1023
2. The electrons identified by quantum numbers n and l :
1) n= 4, l = 1 2) n = 4, l = 0 3) n = 3 , l = 2 4) n = 3 , l = 1
Can be placed in increasing order of energy as:
a) 3 < 4 < 2 < 1 b) 4<2<3<1 c) 2 <4 < 1 < 3 d) 1 < 3 < 2 < 1
3. The following configuration represents : 5f1-14 , 6 d0-2, 7S2
a) d-block element b) s-block element c) Lanthanides d) Actinides
4. Find the overlapping which does not result in 𝜎 bond formation if Z axis is the inter nuclear axis :
a) pz – s b) pz – pz c) px- px d) None of these
5. The radius of the second Bohr orbit for hydrogen is :
(Mass of e- = 9.1x10-31 kg charge on e- = 1.6 x 10-19 c permittivity of vacuum = 8.8 x 10 -12
a) 4.76 A0 b) 0.52 A0 c) 2.12 A0 d) 1.65 A0
6. The correct order of ionic radii of Li+ , Mg2+ , Na+ and Be2+ is : -
a) Be2+< Li+< Mg2+<Na+ b) Be2+<Mg2+< Li+< Na+
b) c) Li+< Be2+<Mg2+<Na+ d) Be2+<Mg2+< Na+<Li+

7. During the following change in structure O =N – O the property which remains the same is :
a) formal change at nitrogen atom
b) octet of nitrogen and oxygen atom
c) Bond angle
d) All of above mentioned properties
1

8. 6.02 x 10 20 molecules of urea are present in 100 ml of its solution. The concentration of urea
solution is : (M.M or urea =60u)
a) 0.001M b) 0.1 M c) 0.01 M d) 0.02 M
9. A d-subshell containing four unpaired electrons can exchange:
a) Four electrons b) three electrons
c) sixteen electrons d) six electrons
10. Difference of electrons between Uub element and Uno element is:
a) 2 b) 4 c) 6 d) 8
11. The velocity of deBroglie wave is given by
𝐶2 ℎ𝑣 𝑚𝑐 2
a) 𝑉 b)𝑚𝑐 c) ℎ
d) v𝜆

12. Two hybrid orbitals have a bond angle of 120 0. The percentage of p-character in the hybrid
orbital is nearly:
a) 25% b) 66% c) 33% d) 50%
In the questions given below, two statements are given one labelled Assertion (A) and the
other labelled Reason (R).
Select the correct answer to these questions from the codes (a), (b), (c) and (d) given below:
(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 correct but R is wrong.
(d) A is wrong but R is correct.

13. Assertion (A): 1 g oxygen and 1 g ozone have equal number of atoms
Reason (R): Mass of one mole atom is equal to its gram atomic mass.
14. Assertion (A): For the outer most electron in Na atom, the orbital angular momentum is zero
Reason(R): For 3s electron, l = 0 and orbital angular momentum is zero

15. Assertion (A): The radius order for an element is rv> rM >rc
Reason (R): During the van der Waal radius measurement the overlap is maximum.
16. Assertion (A): ClF3 has T-shaped structure
Reason (R): It has two lone pairs arranged at an angle of 180◦
SECTION – B
17. Write the difference between 1g atom of nitrogen and 1 g of nitrogen. [1+1=2]
18. How emission and absorption spectrum are different. Explain. (Give at least two points of each)
19. Write four characteristic properties of d- block elements.
20. (a) Hydrogen atom has only one electron yet its spectra contains a large number of lines why?

(b) By what quantum number an atomic orbital is specified?
OR
(a) Why there are no 2d and 3f orbitals?
(b) Why Pauli’s principle is called exclusion principle?
2

21. On the basis of quantum numbers justify the presence of 18 (eighteen) elements in 5th and 32
(thirty-two) elements in 6th period.
SECTION – C
22. a) Define molality.
b) The density of 3 M solution of KCl is 1.25 g ml -1. Calculate molality of the solution.
(K=39, Cl = 35.5)
23. a) Define wave number.
b) Calculate the wave number and frequency of radiation having wavelength 5800 Å.
(C=3x108 𝑚/𝑠)
24. a) Define van der Waal radius.
b) What is the basic difference between the term electron gain enthalpy and electronegativity.
[1+2=3]
25. Answer the following questions. (Give reasons)
a) CO2 and SO2 both are triatomic molecules, but there is big difference in their dipole moment.
Why?
b) Sigma bond is stronger than 𝜋 bond.Why?
c) Why Be2 molecule does not exist? (Explain using M.O Theory.)
26. a) Define the term ionization enthalpy.
b) Write the factors affecting ionization enthalpy of the element by giving suitable examples.
27. 6.02 x 1022 Molecules of N2 present in container, 700mg of N2 are removed. What is the amount
of H2(in grams) required to convert the remaining N2 into NH3?
28. What is dipole moment? Why is the dipole moment of NH 3 is more than that of NF3. Explain.
SECTION – D
The following questions are case-based questions. Read the case carefully and answer the
questions that follow.
29. deBroglie in 1927 suggested that matter and therefore electron, has a dual character that is
both a material particle and a wave. He even derived the mathematical expression λ = h/mv for
calculating the wavelength. It was experimentally verified by Davission and Germer observed
that a beam of electrons is diffracted by a nickel crystal. The wavelengths of the electrons
determined by the diffraction experiment were found to be in agreement with the values
predicted by the deBroglie relation.
Answer the following questions:-
1. de-Broglie equation is obtained by combination of which of the following theories?
a) Planck’s quantum theory

b) Einstein theory
c) Both Planck’s quantum and Einstein theory
d) Theory of interference and diffraction.
OR
For particle, having same kinetic energy the de-Broglie wavelength is:
3

a) Directly proportional to its velocity
b) Independent of velocity and mass
c) Inversely proportional to its velocity
d) None of these

2. The wavelength of matter wave associated with the body of a mass 1000g moving with a
velocity of 100m/s is: (Given: h = 6.6 x 10-34 Js)
a) 6.6× 10-39 cm
b) 6.6× 10-36 cm
c) 6.6× 10-36m
d) 3.31 × 10-32m

3. Write difference between a matter wave and electromagnetic wave.
(Give at least two points )
30. Broadly speaking, there are two types of bonds between atoms. Ionic bond in which electrons
are transferred between atoms and the bond arises from the coulombic interactions between
the resulting ions. Covalent bond in which electron pairs are shared more or less equally
between neighboring atoms. The idea of a dative bond or covalent – coordination bond, in which
one partner donates both the electrons of the shared pair, symbolized by BA, is now obsolete
and the term covalent bond signifies that a bond has been formed by electron sharing
irrespective of the donor of the electron pair. A covalent bond is further classified as polar
covalent bond and a non polar covalent bond.
Now answer the following questions.
i) Covalent bonds are directional bonds. Why?
ii) Write the correct order of bond angles (smallest first) in: H 2S, NH3, BF3 and SiH4
iii) Amongst LiF and LiI which has more covalent character and why?
OR
List properties of ionic compounds affected by polarization. (at least two).
SECTION - E

31. a) How molecular formula and empirical formula of a compound are different?
b) Find the empirical formula of a substance whose composition includes hydrogen, carbon,
oxygen and nitrogen in the mass ratio 1:3:4:7
(Give atomic mass of H=1, C=12, O=16, N=14).
OR
a) What is limiting reactant or limiting reagent?
b) In the reaction:
2A + 4B 3C + 4D
When 5 moles of A react with 6 moles of B then find:
(i) Which is the limiting Reagent.

(ii) Calculate amount of C formed? [1+1=2]
c) An organic compound contains carbon, hydrogen and oxygen.Its elemental analysis gave
C 38.71% and H 9.67%, Find the empirical formula of the compound. (Atomic Mass: C=12,
H=1, 0=16)
4

32. a) State Heisenberg’s uncertainty principle.
b) How Heisenberg uncertainty principle rules out the existence of definite path or
trajectories. Explain.
c) Calculate the uncertainty in the velocity of a wagon of mass 2000 Kg whose position is
known to an accuracy of ± 10m (h = 6.6 x 10 -34 J.s)
OR
a) An electron moves in an electric field with a kinetic energy of 2.5 eV. What is the
associated de-Broglie wavelength? (mass of electron = 9.1 x 10−31 𝑘𝑔)
b) Calculated the wavelength of third line in the Brackett series for hydrogen
(RH = 10.97 x 106 𝑚 −1 )
c) The ionization energy of He+ is 19.6 ×10-18 J/atom. Calculate the energy of second
stationary state in Li2+ ion. (atomic No He = 2, Li=3)
33. a) Define bond order.
b) Write the conditions for the combination of atomic orbitals to form M.O
c) Compare the relative stability and indicate their magnetic properties of super oxide ion O−1
2
and peroxide ion. O2−
2 (Oxygen atomic No. – 8)
OR
a) Define the term hybridisation what is the hybridisation of the central atom in ClF 3 & BrF5
b) Write M.O configuration of oxygen and nitrogen molecule. Find their relative stabilities and
their magnetic behaviour. ( atomic number 0=8, N=7)

5

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