Skip to main content

Gases MCQs for MDCAT Practice

Chemistry section, Gases chapter. Up to eight free sample questions, each with the correct answer and a worked explanation. The full chapter opens in the app.

The bank has 832 active questions on this chapter. Your first 500 practice attempts are free, and every attempt includes a worked explanation.

  1. Question 1
    Under which of the following physical conditions does a real gas approach ideal behavior?
    • High temperature and high pressure.
    • Low temperature and high pressure.
    • High temperature and low pressure. (correct answer)
    • Low temperature and low pressure.
    Correct answer: C
    Real gases approach ideal behavior at high temperatures and low pressures. This minimizes intermolecular forces and particle volume relative to container volume.
  2. Question 2
    The density of a gas X is 6 times the density of a gas Y. If the molecular mass of X is M then what will be the molecular mass of Y?
    • M/6 (correct answer)
    • 2M
    • 6M
    • 6/M
    Correct answer: A
    This question tests the relationship between gas density and molecular mass using the ideal gas law, emphasizing inverse proportionality.
  3. Question 3
    Which of the following shows marked deviation from ideal behaviour at given temperature and pressure.
    • CO2 (correct answer)
    • He
    • H2
    • N2
    Correct answer: A
    Gases deviate from ideal behavior due to intermolecular forces and finite molecular volume; CO2 deviates most due to its polarity and size.
  4. Question 4
    Real gasses behave Ideally at:
    • Low temperature and low pressure
    • Moderate temperature and low pressure
    • High temperature and high pressure
    • High temperature and low pressure (correct answer)
    Correct answer: D
    Real gases approximate ideal behavior under conditions that minimize intermolecular forces and particle volume compared to container volume.
  5. Question 5
    In gases & Liquid, Temperature tells about
    • Average Rotational Kinetic Energy
    • Average Translational Kinetic Energy (correct answer)
    • Average Vibrational Kinetic Energy
    • All of these
    Correct answer: B
    Temperature in gases and liquids is defined by the average kinetic energy of particles, specifically their translational motion.
  6. Question 6
    How much pressure in Nm-2 is exerted by one mole of gas enclosed in a vessel of volume 59.4 m3 at 120°C? (Note: R = 8.314 JK-1 mol-1)
    • 16.79 Nm-2
    • 21.41Nm-2
    • 38.21Nm-2
    • 55.01Nm-2 (correct answer)
    Correct answer: D
    This question tests the application of the Ideal Gas Law to calculate pressure, emphasizing unit consistency and temperature conversion.
  7. Question 7
    If the volume of a gas collected at a temperature of 600 °C and pressure of 1.05 × 105 Nm-2 is 60 dm3, what would be the volume of gas at STP (P=1.01 × 105 Nm-2, T = 273 K)?
    • 100 dm3
    • 75 dm3
    • 19.5 dm3 (correct answer)
    • 51 dm3
    Correct answer: C
    Apply the combined gas law to calculate the final volume of a gas under STP conditions, given initial temperature, pressure, and volume. Converts Celsius to Kelvin correctly.
  8. Question 8
    If a graph is plotted between pressure on x- axis and volume on y- axis for Boyle's law verification, the curve obtained is called
    • Pseudotherm
    • Isotherm (correct answer)
    • Biotherm
    • All of these
    Correct answer: B
    A P-V graph for Boyle's Law verification is an isotherm, representing a state of constant temperature.

Practise all 832 Gases questions

A free account keeps your correct, incorrect and unseen questions separate, and shows the explanation after every attempt.

Create a free account

Read the full Gases chapter notes: Gases notes. Or browse every chapter.