Free Gases MCQs with Answers
443 Gases MCQs from Chemistry, each with the correct answer and a written explanation of why it is correct. Free and unlimited, with no account needed.
Gas behaviour is explained through the kinetic molecular theory and the relationships among pressure, volume and temperature. Work includes STP, Boyle's and Charles's laws, absolute zero, the ideal gas equation, and the distinction between ideal and real gases, especially the effects of intermolecular forces and molecular volume.
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- A. directly proportional to its pressure
- B. inversely proportional to its pressure
- C. independent of its pressure
- D. proportional to the square of its pressure
Explanation: Boyle's law gives PV equal to a constant, so doubling the pressure halves the volume.
Correct answer: inversely proportional to its pressure- A. 200 cm3
- B. 250 cm3
- C. 1250 cm3
- D. 100 cm3
Explanation: Applying P1V1 equal to P2V2 gives V2 equal to 2 times 500 divided by 5, which is 200 cm3.
Correct answer: 200 cm3- A. 25 degrees C and 1 atm
- B. 0 degrees C and 1 atm
- C. 0 K and 1 atm
- D. 25 degrees C and 760 mm of mercury above atmospheric
Explanation: STP is 273.15 K, which is 0 degrees Celsius, at a pressure of 1 atmosphere or 760 mm of mercury.
Correct answer: 0 degrees C and 1 atm- A. 0 degrees C
- B. -100 degrees C
- C. -273.15 degrees C
- D. -373 degrees C
Explanation: Extrapolating the straight line of volume against temperature backwards, every gas reaches zero volume at minus 273.15 degrees Celsius…
Correct answer: -273.15 degrees C- A. 54 degrees C
- B. 300 degrees C
- C. 327 degrees C
- D. 600 degrees C
Explanation: Charles's law must be applied in kelvin, so the initial temperature is 27 plus 273, which is 300 K.
Correct answer: 327 degrees C- A. Gas molecules attract one another strongly
- B. The volume of the molecules themselves is negligible compared with the volume of the container
- C. Collisions between molecules lose energy as heat
- D. The molecules all move at the same speed
Explanation: The ideal model treats molecules as point masses with negligible volume and no intermolecular forces, colliding perfectly elastically so…
Correct answer: The volume of the molecules themselves is negligible compared with the volume of the container- A. pressure
- B. absolute temperature
- C. volume
- D. molar mass
Explanation: Average kinetic energy equals three halves of kT, so it is fixed by absolute temperature alone.
Correct answer: absolute temperature- A. high temperature and low pressure
- B. low temperature and high pressure
- C. high temperature and high pressure
- D. standard temperature and pressure
Explanation: At high pressure the molecules are close enough that their own volume is no longer negligible, and at low temperature they move slowly…
Correct answer: low temperature and high pressure- A. the volume occupied by the gas molecules
- B. the intermolecular forces of attraction
- C. the number of moles present
- D. the temperature of the gas
Explanation: The term involving a raises the measured pressure to what it would have been without attractions pulling molecules away from the wall, so…
Correct answer: the intermolecular forces of attraction- A. 5.6 dm3
- B. 11.2 dm3
- C. 22.4 dm3
- D. 44.8 dm3
Explanation: One mole of any ideal gas occupies 22.4 dm3 at STP, so half a mole occupies 11.2 dm3.
Correct answer: 11.2 dm3- A. Gas molecules are in constant random motion
- B. Collisions between molecules are perfectly elastic
- C. There are strong attractive forces between gas molecules
- D. The volume of the molecules is negligible compared with the volume of the container
Explanation: An ideal gas is defined by the absence of intermolecular forces, which is precisely why it obeys the gas laws exactly.
Correct answer: There are strong attractive forces between gas molecules- A. the weight of the gas molecules
- B. collisions of the molecules with the walls
- C. attraction between molecules and the walls
- D. the chemical reaction of the gas with the walls
Explanation: Each collision delivers a small impulse, and the enormous number of collisions per second averages out into a steady pressure.
Correct answer: collisions of the molecules with the walls- A. double its volume
- B. halve its volume
- C. leave the volume unchanged
- D. quadruple its volume
Explanation: Boyle's law states that pressure and volume are inversely proportional at constant temperature, so the product PV stays constant and…
Correct answer: halve its volume- A. 250 cm3
- B. 500 cm3
- C. 1000 cm3
- D. 1500 cm3
Explanation: Using P1V1 equals P2V2, the new volume is 2 multiplied by 500 divided by 1, which is 1000 cm3.
Correct answer: 1000 cm3- A. inversely proportional to the absolute temperature
- B. directly proportional to the absolute temperature
- C. independent of temperature
- D. proportional to the square of the temperature
Explanation: Volume rises in direct proportion to absolute temperature, so a graph of V against T in kelvin is a straight line that extrapolates back…
Correct answer: directly proportional to the absolute temperature- A. 400 cm3
- B. 1411 cm3
- C. 200 cm3
- D. 600 cm3
Explanation: Converting to kelvin gives 300 K and 400 K, and the volume scales in the same ratio, so 300 multiplied by 400 divided by 300 gives 400…
Correct answer: 400 cm3- A. the volume of an ideal gas extrapolates to zero
- B. water freezes
- C. all gases liquefy
- D. pressure becomes infinite
Explanation: Extending the straight line of a volume against temperature graph backwards, it meets the axis at minus 273.15 degrees Celsius, which is…
Correct answer: the volume of an ideal gas extrapolates to zero- A. PV equals nRT
- B. PV equals nR divided by T
- C. P divided by V equals nRT
- D. PVT equals nR
Explanation: The equation combines Boyle's, Charles's and Avogadro's laws into one relation, with R the universal gas constant at 8.314 J per mole per…
Correct answer: PV equals nRT- A. 22.4 dm3
- B. 44.8 dm3
- C. 11.2 dm3
- D. 24 dm3
Explanation: One mole occupies 22.4 dm3 at STP, so two moles occupy twice that, which is 44.8 dm3.
Correct answer: 44.8 dm3- A. 25 degrees Celsius and 1 atm
- B. 0 degrees Celsius and 1 atm
- C. 0 K and 1 atm
- D. 100 degrees Celsius and 1 atm
Explanation: STP is 273.15 K, that is 0 degrees Celsius, at one atmosphere, and it is under these conditions that a mole of gas occupies 22.4 dm3.
Correct answer: 0 degrees Celsius and 1 atmGases MCQs: common questions
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