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NEET Physics: Avogadro's number Practice Questions

15 free multiple-choice questions on Avogadro's number (Kinetic Theory of Gases) for NEET Physics, each with the correct answer and a step-by-step explanation. Attempt a question, then reveal the solution to check your reasoning.

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  1. Q1. If N_A is the number of particles in one mole, what does a quantity of 1 mole represent?

    • AThe total mass of the substance
    • BThe total number of particles of that substance
    • CThe total volume occupied by the substance
    • DThe total energy of the substance
    Show answer & explanation

    Correct answer: B — The total number of particles of that substance

    One mole represents a specific macroscopic amount of matter, defined by the number of particles (6.022 × 10²³) present in that amount.

  2. Q2. One mole of any ideal gas occupies a volume of approximately:

    • A100 L
    • B22.4 L
    • C11.2 L
    • D22.4 m³
    Show answer & explanation

    Correct answer: B — 22.4 L

    At Standard Temperature and Pressure (STP), one mole of any ideal gas occupies a volume of 22.4 Liters.

  3. Q3. What is the significance of Avogadro's number (N_A)?

    • AThe mass of one mole of any gas
    • BThe volume occupied by one mole of any gas
    • CThe pressure exerted by one mole of gas
    • DThe number of molecules present in one mole of any gas
    Show answer & explanation

    Correct answer: D — The number of molecules present in one mole of any gas

    Avogadro's number is the number of constituent particles (atoms or molecules) contained in one mole of any substance.

  4. Q4. In one mole of carbon dioxide (CO₂), how many molecules are present?

    • A6.022 × 10²²
    • B6.022 × 10²³
    • C1.008 × 10²³ molecules
    • D6.022 × 10²³ molecules
    Show answer & explanation

    Correct answer: D — 6.022 × 10²³ molecules

    One mole of any substance contains 6.022 × 10²³ particles (molecules in this case).

  5. Q5. Avogadro's number (N_A) is defined as the number of molecules present in one mole of any ideal gas at a given temperature and pressure. What is the approximate value of N_A in terms of 6.022 × 10²³ molecules per mole?

    • A6.022 × 10²⁴
    • B6.022 × 10²⁵
    • C6.022 × 10²²
    • D6.022 × 10²³
    Show answer & explanation

    Correct answer: D — 6.022 × 10²³

    Avogadro's number (N_A) is defined as the number of constituent particles (molecules) contained in one mole of a substance. The standard value is 6.022 × 10²³ mol⁻¹.

  6. Q6. How many molecules are present in one mole of an ideal gas?

    • A6.022 × 10²³
    • B6.022 × 10²⁴
    • C6.022 × 10²³ molecules/K
    • D6.022 × 10²³ molecules/mol
    Show answer & explanation

    Correct answer: A — 6.022 × 10²³

    By definition, one mole of any substance contains Avogadro's number of particles, which is approximately 6.022 × 10²³.

  7. Q7. If a gas sample has 6.022 × 10²³ molecules, what is the number of moles of this sample?

    • A0.5 mole
    • B10²³ moles
    • C6.022 × 10²³ moles
    • D1 mole
    Show answer & explanation

    Correct answer: D — 1 mole

    Since 6.022 × 10²³ molecules constitute exactly one mole, the number of moles is 1 mole.

  8. Q8. The factor N_A is essential for converting between the macroscopic scale (moles) and the microscopic scale (number of particles) in the study of gases. What relationship does it establish?

    • AForce and Acceleration
    • BMass and Volume
    • CPressure and Temperature
    • DMoles and Molecules
    Show answer & explanation

    Correct answer: D — Moles and Molecules

    Avogadro's number provides the fundamental link between the mole (a measure of amount) and the number of particles (the microscopic count) of a substance.

  9. Q9. The value of Avogadro's number (N_A) is approximately:

    • A6.022 × 10²³ mol
    • B6.022 × 10²³ g/mol
    • C6.022 × 10²³ kg
    • D6.022 × 10²³
    Show answer & explanation

    Correct answer: A — 6.022 × 10²³ mol

    Avogadro's number (N_A) is the number of particles that make up one mole, meaning 1 mol of any substance contains 6.022 × 10²³ particles.

  10. Q10. If the volume occupied by n moles of an ideal gas is V, and the volume occupied by n+1 moles is V', the relationship between V and V' is:

    • AV' = V + N_A
    • BV' = V + V_A
    • CV' = (n+1)V
    • DV' = V + V
    Show answer & explanation

    Correct answer: D — V' = V + V

    Since volume is directly proportional to the number of moles (at constant T and P), the difference in volume corresponds to the volume of one mole (V_A).

  11. Q11. If two different ideal gases, Gas A and Gas B, are kept at the same temperature and pressure, what is the relationship between the number of moles and the number of molecules of each gas?

    • AThe number of molecules in Gas A is directly proportional to the number of molecules in Gas B.
    • BThe number of moles is inversely proportional to the number of molecules.
    • CThe number of molecules is independent of the number of moles when T and P are constant.
    • DThe number of moles is directly proportional to the number of molecules for both gases.
    Show answer & explanation

    Correct answer: D — The number of moles is directly proportional to the number of molecules for both gases.

    According to the Kinetic Theory of Gases, the number of molecules (N) is directly proportional to the number of moles (n) of the gas. Since temperature (T) and pressure (P) are held constant, the relationship between moles and molecules is linear and directly proportional.

  12. Q12. The molar volume of any ideal gas at STP is:

    • A1 m³
    • B1 liter
    • C224000 L
    • D224000 cm³
    Show answer & explanation

    Correct answer: D — 224000 cm³

    By definition, one mole of any ideal gas occupies a volume of 224000 cm³ (or 22.4 L) at Standard Temperature and Pressure (STP).

  13. Q13. If N molecules of an ideal gas occupy a volume V at a specific temperature and pressure, what is the relationship between N and the amount of substance (moles)?

    • AN = V · N_A
    • BN = PV/RT
    • CN = PV/N_A
    • DN = V/N_A
    Show answer & explanation

    Correct answer: D — N = V/N_A

    The number of molecules (N) is related to the amount of substance (n or moles) by the equation N = n · N_A.

  14. Q14. If N_A is the number of particles in one mole, how does the number of molecules in 1 mole relate to N_A?

    • AThe number of molecules is N_A × N
    • BThe number of molecules is N_A
    • CThe number of molecules is N_A/N
    • DThe number of molecules is N (where N is the number of particles in the mole)
    Show answer & explanation

    Correct answer: B — The number of molecules is N_A

    By definition, one mole contains exactly N_A particles. Therefore, the number of molecules in 1 mole is N_A.

  15. Q15. If a gas sample contains 6.022 × 10²³ molecules, how many moles of the gas is present?

    • A1 mole
    • B2 moles
    • C0.5 mole
    • D10 moles
    Show answer & explanation

    Correct answer: A — 1 mole

    Since Avogadro's number is 6.022 × 10²³ molecules per mole, having 6.022 × 10²³ molecules means the sample contains exactly 1 mole of the gas.

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