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Count moles, molecules or atoms in a given mass or gas volume

This type of question, asked 10 times: 2021 Paper 24, 25 Jun 2022, 26 Jul 2022, 10 Apr 2023, 30 Jan 2024, 3 Apr 2025, 4 Apr 2026 S1, 4 Apr 2026 S2, 6 Apr 2026 S2, 8 Apr 2026 S2. All 10 questions below, oldest first.

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  1. Question 1

    2021 Paper 24

    55
    The number of atoms in 8 g8\text{ }g of sodium is x×1023x \times10^{23}. The value of xx is (Nearest integer) [Given: NA=6.02×1023 mol−1N_{A}= 6.02 \times10^{23}{\text{ }mol}^{- 1} Atomic mass of Na=23.0u]Na = 23.0u\rbrack

  2. Question 2

    25 Jun 2022

    51
    The number of NN atoms in 681 g681\text{ }g of C7H5 N3O6C_{7}H_{5}{\text{ }N}_{3}O_{6} is x×1021x \times10^{21}. The value of xx is (NA=6.02×1023 mol−1)\left( N_{A}= 6.02 \times 10^{23}\text{ }mol^{- 1} \right) (Nearest Integer)

  3. Question 3

    26 Jul 2022

    121
    Hemoglobin contains 0.34%0.34\% of iron by mass. The number of FeFe atoms in 3.3 g3.3\text{ }g of hemoglobin is (Given : Atomic mass of FeFe is 56 u56\text{ }u, NA=6.022×1023 mol−1N_{A} = 6.022 \times 10^{23}\text{ }mol^{- 1})

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  4. Question 4

    10 Apr 2023

    46
    The number of molecules and moles in 2.8375 litres of O2O_{2} at STP are respectively

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  5. Question 5

    30 Jan 2024

    58
    0.05 cm0.05\text{ }cm thick coating of silver is deposited on a plate of 0.05 m20.05{\text{ }m}^{2} area. The number of silver atoms deposited on plate are ____ ×1023\times10^{23}. (At mass Ag =108, d=7.9 g cm−3= 108,\text{ }d = 7.9\text{ }g{\text{ }cm}^{- 3} )

  6. Question 6

    3 Apr 2025

    33
    Among 10−9 g10^{- 9}\text{ }g (each) of the following elements, which one will have the highest number of atoms? Element: Pb,Po,PrPb,Po,Pr and Pt

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  7. Question 7

    4 Apr 2026 S1

    26
    Number of moles and number of molecules in 1.4187 L of SO2SO_{2} at STP respectively are

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  8. Question 8

    4 Apr 2026 S2

    26
    The correct order of total number of atoms present in (A) 2 moles of cyclohexane (B) 684 g of sucrose (C) 90.8 L of dihydrogen at STP

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  9. Question 9

    6 Apr 2026 S2

    26
    Which of the following contain the same number of atoms? (Given : Molar mass in gmol−1gmol^{- 1} of H,He,OH,He,O and S are 1,4,161,4,16 and 32 respectively) (A) 2 g of O2O_{2} gas (B) 4 g of SO2{SO}_{2} gas (C) 1400 mL of O2O_{2} at STP (D) 0.05 L of He at STP (E) 0.0625 mol0.0625\text{ }mol of H2H_{2} gas Choose the correct answer from the options given below :

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  10. Question 10

    8 Apr 2026 S2

    26
    Match List-I with List-II.
    List-I Mass of substanceList-II Number of atoms
    (A)1.8mg1.8mg water(I)
    2×10−4×NA2 \times 10^{- 4} \times N_{A}
    (B)9.8mg9.8mg sulphuric acid(II)
    1.5×10−4×NA1.5 \times 10^{- 4} \times N_{A}
    (C)1.8 mg carbon(III)
    3×10−4×NA3 \times 10^{- 4} \times N_{A}
    (D)5.85 mg salt (NaCl)(NaCl)(IV)
    7×10−4×NA7 \times 10^{- 4} \times N_{A}
    Choose the correct answer from the options given below:

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