Class 11 PT I Question Paper 2025-26 Chemistry

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PT-1 SESSION 2025-26
Class-11
TIME-90 MIN​ SUBJECT- CHEMISTRY M.M.-40
1. The significant figures in 0.00051 are ————–.

(a) 5 (b) 3 (c) 2 (d) 26

2.Which of the following pairs of gases contains the same number of molecules?

(a) 16 g of O2 and 14 g of N2

(b) 6 g of O2 and 22 g of CO2

(c) 28 g of N2 and 22 g of CO2

(d) 32 g of CO2 and 32g of N2

3. The empirical formula and molecular mass of a compound are CH2O and 180 g
respectively. What will be the molecular formula of the compound?
(a) C9H18O9 (b) CH2O (c) C6H12O6 (d) C2H4O2
4.. Which one will have maximum number of water molecules?
(a) 18 molecules of water (b) 1.8 grams of water

(c) 18 grams of water (d) 18 moles of water

5. Principal, Azimuthal and magnetic quantum numbers are respectively related to:

(a) Size, shape and orientation (b) Shape, size and orientation

(c) Size, orientation and shape (d) None of the above

6. The electronic configuration of chromium (Z=24) is:

(a) [Ne] 3s2 3p6 3d4 4s2 (b) [Ne] 3s2 3p6 3d5 4s1

(c) [Ne] 3s2 3p6 3d1 4s2 (d) [Ne] 3s2 3p6 4s2 4p4

7. Which of the following is not permissible?

(a) n= 4, l = 3, m= 0 (b) n= 4, l = 2, m= 1

(c) n= 4, l = 4, m= 1 (d) n= 4, l = 0, m= 0

8.According to Aufbau's principle, which of the following orbital should be filled first?

(a)5d (b) 4p (a) 3p (a) 2s

Directions : Each of these questions contain two statements, Assertion and Reason.
Each of these questions also has four alternative choices, only one of which is the
correct answer. You have to select one of the codes (a), (b), (c) and (d) given below.​
(a) Assertion is correct, reason is correct; reason is a correct explanation for
assertion.​
(b) Assertion is correct, reason is correct; reason is not a correct explanation for
assertion​
(c) Assertion is correct, reason is incorrect​
(d) Assertion is incorrect, reason is correct.
9. Assertion : It is impossible to determine the exact position and exact momentum of
an electron simultaneously.​
Reason : The path of an electron in an atom is clearly defined.
10.Assertion: One mole of SO2 contains double the number of molecules present in
one mole of O2.​
Reason: Molecular weight of SO2 is double to that of O2.
Very Short Answer (2 mark each)
11. State the differences between molarity and molality..
12.State law of multiple proportion with suitable example?
13 If the initial volume is 2 litres, the initial molarity is 6M and the final volume is 6
litres. Find the Final Molarity. Consider final molarity to be M2.
14. Define photoelectric effect. How do intensity and frequency of light affects the
photoelectric effect.
15.Write all the possible set of quantum numbers for the last electron of sodium and
chlorine.
(3 marks each)
16. Calculate the velocity of an electron if its position is known with an uncertainty of
10-10 m (given h = 6.626 x 10-34 Js and mass of electron = 9.1 x 10-31 kg).
17.Write (i) Aufbau principle (ii) Hunds rule (iii) Pauli’s exclusion principle
18. The Balmer series in the hydrogen spectrum corresponds to the transition from
n₁ = 2 to n₂ = 3,4,… This series lies in the visible region. Calculate the wave number
of the line associated with the transition in the Balmer series when the electron
moves to n = 4 orbit. (RH = 109677 cm-¹)

19.What is limiting reagent? In the reaction 2A + 4B → 3C + 4D, when 5 moles of A

react with 6 moles of B, then (i) Which is the limiting reagent? (ii) Calculate the
amount of C formed?
20. A compound contains 4.07% hydrogen, 24.27% carbon, and 71.65% chlorine. Its
molar mass is 98.96 g/mol. Determine its empirical and molecular formula.

(5 marks)
21(a).Write electronic configuration of the following (i) S (ii) F (iii) K (iv) Cr (v) Cu
(vi) Mg

21(b). Arrange the following orbitals in the increasing order of energy

.(a) 1s, 2s, 3s, 3p
(b) 4s, 3s, 3p, 4d
Or
21. According to de Broglie, the matter should exhibit dual behaviour, that is, both
particle and wave like properties. However, a cricket ball of mass 100 g does not
move like a wave when it is thrown by a bowler at a speed of 100 km/h. Calculate
the wavelength of the ball and explain why it does not show wave nature.

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