CBSE Class 11 Chemistry PT-1 Question Paper 2025-26: St. Margaret School, Rohini

11th Class CBSE Board Chemistry PT-01 SET B Examination (2025-26): St. Margaret Sr. Sec. School, Prashant Vihar, Sector 14, Rohini, Delhi-85 India

School Name:	St. Margaret Sr. Sec. School, D-BLOCK, Prashant Vihar, Sector 14, Rohini, New Delhi 110085 India
Class:	11th Standard (CBSE)
Subject:	Chemistry
Time Duration:	01 Hours
Maximum Marks:	25
Date:	~ June – July, 2025

SECTION – A

MCQ (1 mark each)

Question 01: The number of atoms present in 1.6 g of sulphur (atomic mass = 32 u) is:

1. 6.022 x 10²³
2. 3.011 x 10²²
3. 1.204 × 10²³
4. 6.022 x 10²²

Question 02: Which of the following pairs does not obey the law of multiple proportions?

1. H₂O and H₂O₂
2. CO and CO₂
3. CO₂ and SO₂
4. NO and NO2₂

Question 03: The number of significant figures in 100000 are:

1. 4
2. 1
3. 6
4. 2

Question 04: A hydrocarbon was found to contain 75% by mass of carbon and 25% by mass or hydrogen. What is the empirical formula of the compound?

1. C₂H₄
2. C₂2H₆
3. CH₄
4. C₆H₆

Question 05: Which of the following represents the correct set of quantum numbers for an electron in 4d orbital?

1. n = 4, i = 1
2. n = 4, i = 2
3. n = 4, i = 0
4. n = 4, i = 3

Question 06: Paschen series belong to

1. UV region
2. IR region
3. Visible region
4. None of these

Question 07: What will be the molarity of a solution which contains 5.85 g of NaCl(s) per 500 mL?

1. 4 mol L⁻¹
2. 20 mol L⁻¹
3. 0.2 mol L⁻¹
4. 2 mol L⁻¹

Question 08: Bohr’s model can explain:

1. The spectrum of the H atom only
2. Spectrum of atom or ion having one electron
3. The spectrum of hydrogen molecule
4. Solar spectrum

Section – B: Short Answer Questions

(2 marks each)

Question 09: Calculate the number of moles in 22 g of CO₂. (Molar mass of CO₂ = 44 g / mol)

Question 10: How many grams of KCIO₃ must be decomposed to prepare 3.36 litres of oxygen at STP? (Atomic weight of K = 39, Cl = 35.5, O = 16 u)

Question 11: Using ‘s’, ‘p’, ‘d’, ‘f’ notations, describe the orbital with the following quantum numbers.

1. n = 2, I = 1
2. n = 4, / = 0
3. n= 5, / = 3
4. n = 3, / = 2

Section – C:

(3 marks each)

Question 12: Calculate the number of atoms of Na, C and O in 5.3 g of sodium carbonate (Na₂CO₃). (Atomic masses: Na = 23, C = 12, O = 16)

Question 13: How many photons of light having a wavelength of 500 nm would provide 1.2 J of energy?
(h = 6.63 x 10^-34 J s; c = 3.00 x 10⁸ m s^-1)

Section – D:

(5 marks)

Question 14:

(a) An atomic orbital has n = 3. What are the possible values of / and m?

(b) Write the electronic configuration of an element with atomic number 25.

(c) Calculate the wavelength of a photon emitted during a transition from n = 5 state to n = 2 state in the hydrogen atom? 1+1+3