Class 11 Half Yearly Question Paper 2025-26 Chemistry

CBSE CLASS 11
Half Yearly Question Paper
Session 2025-26

CHEMISTRY

Exam CBSE Class 11
Subject Chemistry
Session 2025-26
Document Type Half Yearly Question Paper

Notes · Sample Papers · Previous Year Papers · Mock Tests

.
.co s e m
em l a

as Question Paper ag

SESSION: 2025 – 2026
CLASS: XI MAXIMUM MARKS: 70
SUBJECT: CHEMISTRY TIME: 3 HOURS
General Instruction:
Read the following instructions carefully:

m
(a) There are 33 questions in this questions paper with internal choice and consists of 7 pages.

co
(b) SECTION A consists of 16 multiple–choice questions carrying 1 mark each.

c om m .
(c) SECTION B consists of 5 very short answer questions carrying 2 marks each.

.
(d) SECTION C consists of 7 short answer questions carrying 3 marks each.

m s e
e l a
(e) SECTION D consists of 2 case-based questions carrying 4 marks each.

l as
(f) SECTION E consists of 3 long answer questions carrying 5 marks each.
ag
g
(g) All questions are compulsory.
a
(h) Use of log table and calculator is not allowed.
(i) 15-minute time has been allotted to read the question paper.

SECTION – A
1. Which one of the following gases will have least volume if 10 g of each gas is taken at 1
the same temperature and pressure?
(a) CO2 (b) N2
(c) CH4 (d) HCl

m
.co
2. In a flask, the weight ratio of CH4 (g) and SO2 (g) at 298 K and 1 bar is 1 : 2. The ratio 1

m (b) 4:1
of the number of molecules of SO2 (g) and CH4 (g) is

s e
(a)1:4
l a
(c)1:2
ag (d) 2:1
3. 1

m
A glucose solution is prepared by mixing two glucose solution of different

m .co
concentrations as shown above. The concentration of newly formed glucose solution

.co em
is:

m la s
(a) 0.056M (b) 0.15M

s e g
la a
(c) 0.079M (d) 0.10M

ag 4. A vessel contains 150g of CaCO . Which one of the following statements is correct
about the substance?
3 1

(a) It contains 2.5 mol of CaCO3.
(b) Total number of atoms present in the given compound is 4.5165 ×1024
(c) On heating it decomposes to produce 3.0 mol of CaO.
(d) 44.8 L of CO2 (at STP) can be obtained by the thermal decomposition.

m . c
1

c. o s e m
s em
Page 1 of 7

5. Match the following Co
olumns: 1

Colum mn –I Column –II
(i) Principal quant ntum number (p) orientation of the orbital
(ii) Azimuthal quantum
qua number (q) energy and size of orbitall
(iii) Magnetic quant ntum number (r) spin of electron
(iv) Spin quantum number (s) shape of the orbital
Choose the correct opti tion:-
(a) (i-q), (ii-s), (iii-p), (ivv-r)
(b) (i-q), (ii-p), (iii-q), (iiv-s)
(c) (i-s), (ii-q), (iii-p), (ivv-r)
(d) (i-r), (ii-s), (iii-p), (ivv-q)

6. Which one of the followowing is responsible for ruling out the existence off definite 1
paths or trajectories of electrons?
e
(a) Pauli’s exclusion Prin
inciple
(b) Heisenberg’s uncertaainty Principle
(c) Hund’s rule of maxim mum multiplicity
(d) Aufbau Principle
7. If the kinetic energy of a moving particle is E, then the de-Broglie wavel
elength is 1
ℎ ℎ
(a) λ= (b) λ=
ℎ √
(c) λ= (d) λ=
√ ℎ

8. The probability density plots
p of 1s and 2s atomic orbital are given in thee following 1
figure:-

The density of dots in a region represents the probability density of findiding
electrons in that region.
On the basis of above ddiagram, which one of the following statements iis
incorrect?
(a) 1s and 2s orbitals aree spherical in shape.
(b) The probability of finnding the electron is maximum near the nucleus. us.
(c) The probability of finnding the electron at a given distance is equal in
n all
directions.
(d) The probability denssity of electrons for 2s orbital decreases uniforml
mly as
distance from the nucleuus increases.
9. Some electrons have fol ollowing quantum numbers, 1
(i) n=4, l=1 (ii) n=4, l=0
(iii) n =3, l=2 (iv) n=3, l=1
Arrange them in the orde der of increasing energy -

2

For more Question Papers, Sample Papers, Notes & Syllabus visit Page 2 of 7

.
.co s e m
em l a

as (a) (iv)<(ii)<(iii)<(i)
ag
(b) (ii)<(iv)<(i)<(iii)
(c) (i)<(iii)<(ii)<(iv) (d) (iii)<(i)<(iv)<(ii)

10. The negative electron gaain enthalpies of halogens follow the order: - 1
(a) F>Cl>Br<I (b) F < Cl >Br<I
(c) F<Cl>Br> I (d) F<Cl<Br<I

11. Isostructural species aree those which have the same shape and hybridizaation. 1

m
Among the given speciees identify the isostructural pairs-

co
(a) [NF3 and BF3] (b) [BF4 – and NH4+]

om .
(d) [NH3 and NO3 –]
c m
(c) [BCl3 and BrCl3]

m . s e
e l a
12. The correct order of bond lengths P, Q and R is 1

l as ag
ag
(a) P> Q>R (b) R>Q>P
(c) Q>P>R (d) Q>R>P
For Questions 13 to 16,16 two statements are given: one labelled as Assertion
As (A)
and the other labelled ed as Reason (R). Select the correct answe wer to these
questions from the cod odes (A), (B), (C) and (D) as given below:

m
(A) Both Assertion (A) aand Reason (R) are true and Reason(R) is the cor
orrect

.co
explanation of Assertion(n(A).

e m
(B) Both Assertion (A) and Reason (R) are true but Reason (R) is not the correct

as
explanation of Assertion
on (A).

l
ag
(C) Assertion (A) is true
ue but Reason (R) is false.
(D) Assertion (A) is falsse but Reason (R) is true.

13. Assertion (A): At 273 K & 1 bar, 22.4 L of both O2 and CO2 contaain an equal 1
number of molecules.
Reason(R): According tto Avogadro’s law, at a constant temperature & pr
pressure
equal volume of all gasees contain an equal number of molecules.

body is an ideal body that emits and absorbs radiiations of all 1
14. Assertion (A): Black bo

m
frequencies.

m .co
.co
Reason(R): The frequequency of radiation emitted by a body goes from
rom a lower

s em
frequency to higher frequ
quency with an increase in temperature.

e m l a
s g elementnt is nearly
15. Assertion (A): Element
nts F, Cl, Br constitute a triad. 1

g la a
a
Reason(R): In a triad of elements, atomic mass of middle
arithmetic mean of the aatomic mass of other two.
16. Assertion (A): Among two O-H bonds in H2O molecule, the energiess required to 1
break the first O-H bond and second O-H bond are the same.
Reason(R): This is beccause the electronic environment around oxyg
gen becomes
different after the breakaage of one O-H bond.

m . c
3

c. o s e m
s em
Page 3 of 7

SECTION – B
-1
17. A table tennis ball has a mass of 10g and a speed of 90 ms . If speed can be 2
measured within an accuracy of 4%, determine the uncertainty in speed and
position.
18. (a) How many singly occupied orbitals are present in Ni atom? 2
(b)What will be the effect of kinetic energy of the photoelectron if we increase-
(i) intensity of light (ii) frequency of light
19. Among the given elements B, Al, C and Si 2
(a) Which element has the highest first ionisation enthalpy and why?
(b) Which element contains the most metallic character? Give reason.

OR

The first ionisation enthalpy of Na is lower than that of Mg. Compare the second
ionisation enthalpy of Na with that of Mg, Justify your answer.
20. Mention the hybridization in case of PCl5.Why are the axial bonds longer as 2
compared to the equatorial bonds in PCl5 ?
21. Write the hybridization of Nitrogen in the following species: 2
-
NO2+, NO3-, NH4+, NH2

SECTION – C
22. A welding machine fuel gas contains carbon and hydrogen only. Burning a small 3
sample of it in oxygen gives 3.38g CO2, 0.690g of water and no other products. A
volume of 10.0L (measured at STP) of this welding gas is found to weigh 11.6g.
Calculate:
(i) Molar Mass of the gas.
(ii) Empirical formula
(iii)Molecular Formula.
OR

(a) Calculate the total number of electrons in 18mL of water. (Density of water
is1g/mL)
(b) Concentrated aqueous solution of sulphuric acid is 98% by mass and has a
density of 1.80g/cc.What is the volume of acid required to make one litre of 0.1M
H2SO4 solution?
23. Calcium carbonate reacts with aqueous HCl to give CaCl2 and CO2 according to the 3
reaction:
CaCO3(s)+2HCl(aq)→CaCl2(aq)+CO2(g)+H2O(l)
What mass of CaCO3 is required to react completely with 25mL of 0.75MHCl?

24. (a) What will be the maximum number of electrons having the same spin in an 3
atom with (n + l) = 4?
(b) Write the total number of angular nodes and radial nodes present in 3p orbital.
(c) The ion of an element has electronic configuration [Ar]3d4 in +3 oxidation state.
Write the electronic configuration of its atom and also identify the element.

4

For more Question Papers, Sample Papers, Notes & Syllabus visit Page 4 of 7

.
.co s e m
em l a

as 25. (a)The graph (given beloow) shows the variation of I.E g
a of some elementss with their 3
Atomic number:

m
om . co
. c e m
m
eO is a basic oxidede and Cl O is an acidic oxide. Justify the statemment with gl as
s
Give reason behind the ddeviation in I.E of some elements from the gener eral trend.

g a
l chemical equationons.
(b) Na 2 2 7
a
a
proper
3– 2– – + 2+ 3+
26. Consider the following sspecies: N , O , F , Na , Mg and Al 3
(a) What is common in tthem?
(b) Arrange them in the order of increasing ionic radii.
(c) Predict the position of
o the element in the periodic table satisfying the
he
1 2
configuration (n- 1)d ns for n=4.

27. Calculate the bond orderr of the following species and also indicate theirr magnetic 3

m
.co
properties: O2, O2 +, O22-- .

m
28. (a)Do you think, hybridi
disation of B & N atom changes in the following reaction,
r 3

s e
justify your answer.

l a
BF3 + NH3 —> F3B.N .NH3

ag
(b) The type of overlapp
pping given in the following figures does not resul
ult in bond
formation,Why?

(c) Among Ammonia annd Phosphine,which one is highly soluble in wateer and why?

m
m .co
.co
SECTION – D

s em
The following question
ons are case-based questions. Each question has
as an

e m l a
internal choice and carrries 4 (1+1+2) marks each. Read the passagee carefully

las and answer the question
ons that follow.
g
a Visible
ag 29. Spectrum is combination
on of radiations of different wavelengths.
continuous spectrum. Attomic spectrum (line spectrum) is discontinuous
spectrum is 4
nuous spectrum.
It can be absorption or emission
e spectrum when energy is supplied to eleectrons,
her energy levels. When they come back to lowerr energy
these get excited to highe
level, they radiate energy
gy in form of bright spectral lines separated by dark
da bands.
Each element has its uni
unique spectrum by which it can be identified.

m . c
5

c. o s e m
s em
Page 5 of 7

(a) Wavelengths of different radiations are given below:
λ(A) =300 nm λ(B)= 300 μm λ(C)= 3 nm λ (D)=30 A0
Arrange these radiations in the increasing order of their energies.
OR
(a) Calculate mass of 1 mole of electrons. (me = 9.1 × 10–31 kg).
(b) En= − 313.6/n2 kcal/mol. If the value of En= − 34.84 kcal/mol, to which value
does 'n' correspond?
(c) What transition in a hydrogen spectrum would have the same wavelength as in
the Balmer transition n=4 to n=2 of He+ spectrum?

30. Modern periodic table arranges the elements in the increasing order of atomic 4
number. It has 18 groups and 7 periods. Atomic numbers are consecutive in a
period and increases in group in a pattern. Elements are divided into four
blocks, s-block, p-block, d-block and f-block based on their electronic
configuration. 78% of elements are metals, about 20 elements are non-metals and
few elements like B, Si, Ge, As are metalloids. Metallic character increases down
the group but decreases along the period from left to right. The physical and
chemical properties vary periodically with their atomic numbers. Periodic trends
are observed in atomic size, ionisation enthalpies, electron gain enthalpies,
electronegativity and valence.

(a) Classification of elements with respect to atomic number is more appropriate
compared to its atomic mass, why?
OR
(a) Atomic radius of noble gases is larger than halogens. Why?

(b)Write the electronic configuration of the element which is just above the
element with atomic number 43 in the same group. Mention the group number.
(c) The ionization enthalpy of sodium is 495kJ/mol. Calculate the energy required
in joules to convert all atoms of sodium in 2.3mg of sodium vapours into Na + ion.

SECTION – E
31. (a) What volume of oxygen at NTP is needed to cause the complete combustion of 5
200 mL of acetylene? Calculate the volume of carbon dioxide formed.
2C2H2 + 5O24CO2 + 2H2O
(b) Calculate the volume of carbon dioxide liberated at STP when 10g of 90%
pure lime stone (CaCO3) is heated.
(c) How many significant figures are there in each of the following numbers:
i) 0.062 ii) 6.022×1023
OR

(a) 5 mol of AB2 weigh 125x10-3 kg and 10 mol of A2B2 weigh 300x10-3 kg.
Calculate the molar mass of A and B.
(b) The ratio of the mass percentage of C and H of an organic compound (CxHyOz)
is 6:1. If one molecule of the above compound (CxHyOz) contains half of the
amount of oxygen that is required to burn one molecule of compound C xHy
completely to CO2 and H2O. State the empirical formula of the compound.

6

For more Question Papers, Sample Papers, Notes & Syllabus visit Page 6 of 7

.
.co s e m
em l a

as ag
32. (a) The threshold frequency vo for a metal is 7.0x1014Hz. Calculate the kinetic 5
15 -1
energy of an electrons emitted when radiation of frequency v = 1.0 x10 s hits
the metal.
(b) Find the number of spectral lines observed when an electron travels from
n=7 to n=2 in a hydrogen atom.
(c) How many electrons will be present in the sub-shells having ms= -1/2 for

m
n=4?

co
OR

c om m .
(a) A cricket ball of mass 100g is thrown by a bowler at a speed of 100 km/h.

m .
Calculate the wavelength of the ball and explain why it does not show wave
s e
s e
nature.
g l a
l a a
(b) The kinetic energy of an electron in the second Bohr orbit of a hydrogen atom

ag
2
ℎ
is . Find the value of x. [ao is the Bohr radius].
𝑥𝜋2 𝑚𝑎20
(c) How much energy is required to ionise a H – atom, if the electron occupies n=5
orbit?

33. (a) Both NH3 and NF3 have identical shapes and same state of hybridisation. Both 5
N-H and N-F bonds have almost the same electronegativity difference. But still,
the two molecules have different dipole moment values. How will you account for
it?

m
.co
(b) Draw the resonating structure of the following:-
(i) Ozone(O3) (ii) Carbonate (CO32-)

e m
as
(c) Using VSEPR theory, draw the structures and write the shape of the following

l
ag
molecules: (i) SF4 (ii) ClF3
OR

(a) Explain the following observation:
(i) NaCl gives a white precipitate with AgNO3 solution but CCl4 does not.
(ii) A molecule of PCl5 exist while that of NCl5 does not.
(iii) Bond angle in NH3 is more than PH3.
(b)

m
m .co
m .co s em
s e g la
la i) Which of the above compounds will have intermolecular a
(I) (II)

ag hydrogen bonding and
which compound is expected to show intramolecular hydrogen bonding?
ii) Which of the above two compounds will show higher melting point? Explain.

***********

m . c
7

c. o s e m
s em
Page 7 of 7