MDCAT Gases MCQs

This comprehensive set of MCQs on Gases is designed to cover all essential topics required for success in the Medical and Dental College Admission Test (MDCAT). Focused on key concepts such as gas laws, kinetic molecular theory, and gas behavior under different conditions, these MCQs are crafted to help aspiring medical and dental students build a strong understanding of gases and their significance in both chemistry and health sciences.

Who should practice Gases MCQs?

Students preparing for the MDCAT who wish to solidify their understanding of the properties and behavior of gases, essential for solving chemistry problems.
Individuals seeking to enhance their knowledge of topics such as Boyle’s law, Charles’s law, Avogadro’s law, and the ideal gas equation, which are important for medical and dental disciplines.
University students targeting high-yield topics like gas diffusion, effusion, and partial pressure.
Anyone aiming to strengthen their grasp of how gases interact and behave under various temperature and pressure conditions, which is relevant to understanding respiratory physiology.
Candidates focused on developing problem-solving skills related to the application of gas laws in real-life medical and scientific scenarios.
Suitable for all students preparing for the MDCAT, including those looking to improve their exam confidence in chemistry and gain a deeper understanding of gas-related principles.

1. Which of the following is a property of gases?

A) Definite shape
B) Definite volume
C) High compressibility
D) High density

View Answer

2. Boyle’s law states that the pressure of a gas is inversely proportional to its:

A) Temperature
B) Volume
C) Number of moles
D) Mass

View Answer

3. Charles’s law states that the volume of a gas is directly proportional to its:

A) Pressure
B) Temperature
C) Density
D) Mass

View Answer

4. The ideal gas equation is expressed as:

A) PV = nRT
B) P/T = V/n
C) P = V/T
D) PV² = RT

View Answer

5. Which of the following assumptions is part of the kinetic molecular theory of gases?

A) Gas particles are in constant random motion
B) Gas particles have strong intermolecular forces
C) Gas particles are stationary
D) The volume of gas particles is significant

View Answer

6. What is the SI unit of pressure used in gas laws?

A) Joule
B) Pascal
C) Newton
D) Liter

View Answer

7. According to Boyle’s law, if the pressure on a gas increases, its volume:

A) Increases
B) Decreases
C) Remains constant
D) Becomes zero

View Answer

8. What is the value of the universal gas constant (R) in the ideal gas equation?

A) 0.0821 atm L/mol K
B) 1 atm L/mol K
C) 8.314 atm L/mol K
D) 0.001 atm L/mol K

View Answer

9. Charles’s law can be expressed mathematically as:

A) V ∝ 1/T
B) V ∝ P
C) V ∝ T
D) V ∝ n

View Answer

10. The temperature in gas law calculations must always be expressed in:

A) Celsius
B) Kelvin
C) Fahrenheit
D) Rankine

View Answer

11. Boyle’s law is applicable when the:

A) Temperature remains constant
B) Pressure remains constant
C) Volume remains constant
D) Number of moles remains constant

View Answer

12. According to the kinetic molecular theory, the average kinetic energy of gas particles is directly proportional to:

A) Volume
B) Pressure
C) Temperature
D) Density

View Answer

13. If the volume of a gas is doubled while the temperature remains constant, what happens to its pressure?

A) It doubles
B) It decreases by half
C) It remains the same
D) It increases fourfold

View Answer

14. Charles’s law describes the relationship between which two variables?

A) Volume and pressure
B) Temperature and pressure
C) Volume and temperature
D) Volume and mass

View Answer

15. The ideal gas law is a combination of which two laws?

A) Boyle’s law and Charles’s law
B) Avogadro’s law and Boyle’s law
C) Dalton’s law and Graham’s law
D) Charles’s law and Graham’s law

View Answer

16. The general gas equation is given by:

A) P₁V₁/T₁ = P₂V₂/T₂
B) PV = nR
C) V = nRT/P
D) PV = R/nT

View Answer

17. The kinetic molecular theory of gases assumes that gas particles:

A) Have attractive forces between them
B) Have elastic collisions
C) Move in curved paths
D) Have significant volumes

View Answer

18. According to Boyle’s law, if a gas at constant temperature has its pressure reduced by half, its volume will:

A) Double
B) Decrease by half
C) Remain constant
D) Become zero

View Answer

19. In the ideal gas equation, what does “n” represent?

A) Number of gas particles
B) Number of moles of gas
C) Pressure of the gas
D) Volume of the gas

View Answer

20. The kinetic molecular theory of gases explains the behavior of gases by assuming that:

A) Gas particles move slowly at room temperature
B) Gas particles move faster at lower temperatures
C) Gas particles exert no forces on each other
D) Gas particles move in circular paths

View Answer

21. According to Charles’s law, if the temperature of a gas increases, its volume:

A) Decreases
B) Increases
C) Remains the same
D) Becomes zero

View Answer

22. What are the standard temperature and pressure (STP) conditions for gases?

A) 0°C and 1 atm
B) 25°C and 1 atm
C) 0°C and 760 mmHg
D) 25°C and 760 mmHg

View Answer

23. Which gas law explains why a balloon expands when heated?

A) Boyle’s law
B) Charles’s law
C) Graham’s law
D) Dalton’s law

View Answer

24. What is the pressure of a gas if 2 moles of gas are confined to a volume of 10 liters at 300 K? (R = 0.0821 atm L/mol K)

A) 4.92 atm
B) 6.15 atm
C) 3.2 atm
D) 2.46 atm

View Answer

25. According to Boyle’s law, the product of pressure and volume for a given mass of gas at constant temperature is:

A) Constant
B) Proportional to the temperature
C) Equal to the volume
D) Zero

View Answer

26. In the ideal gas equation PV = nRT, what does “T” represent?

A) Temperature in Celsius
B) Temperature in Fahrenheit
C) Temperature in Kelvin
D) Temperature in Rankine

View Answer

27. Which of the following gases will diffuse the fastest according to Graham’s law?

A) Oxygen
B) Helium
C) Nitrogen
D) Carbon dioxide

View Answer

28. The general gas equation can be rearranged to solve for the volume of a gas as:

A) V = P₁V₁/T₁
B) V = nRT/P
C) V = nP/R
D) V = RT/P

View Answer

29. What is the pressure exerted by 4 moles of an ideal gas at a temperature of 300 K in a 5 L container? (R = 0.0821 atm L/mol K)

A) 10.02 atm
B) 15.36 atm
C) 19.72 atm
D) 24.62 atm

View Answer

30. Which gas law relates the pressure, volume, and temperature of a gas?

A) Boyle’s law
B) Charles’s law
C) Ideal gas law
D) Avogadro’s law

View Answer

31. According to the kinetic molecular theory, the pressure exerted by a gas is due to:

A) The collisions of gas particles with each other
B) The collisions of gas particles with the walls of the container
C) The attractive forces between gas particles
D) The energy of the gas particles

View Answer

32. Boyle’s law describes the relationship between which two variables?

A) Pressure and volume
B) Volume and temperature
C) Pressure and temperature
D) Volume and mass

View Answer

33. Charles’s law can also be expressed as:

A) V₁T₁ = V₂T₂
B) P₁V₁ = P₂V₂
C) V₁/T₁ = V₂/T₂
D) P₁T₁ = P₂T₂

View Answer

34. At constant pressure, the volume of a gas is proportional to:

A) The pressure
B) The temperature
C) The mass of the gas
D) The number of particles

View Answer

35. The kinetic molecular theory of gases assumes that the collisions between gas particles:

A) Are elastic
B) Cause gas particles to slow down
C) Decrease the energy of the gas
D) Are inelastic

View Answer

36. According to Avogadro’s law, at constant temperature and pressure, the volume of a gas is directly proportional to its:

A) Mass
B) Number of moles
C) Pressure
D) Kinetic energy

View Answer

37. Boyle’s law is mathematically represented as:

A) P₁V₁ = P₂V₂
B) V₁/T₁ = V₂/T₂
C) P₁T₁ = P₂T₂
D) V ∝ n

View Answer

38. According to Charles’s law, if the temperature of a gas is reduced to half, its volume will:

A) Double
B) Remain the same
C) Reduce to half
D) Become zero

View Answer

39. The ideal gas equation can be derived by combining which of the following gas laws?

A) Boyle’s law, Charles’s law, and Avogadro’s law
B) Dalton’s law and Graham’s law
C) Charles’s law and Graham’s law
D) Boyle’s law and Dalton’s law

View Answer

40. What is the value of absolute zero in Celsius, according to the kinetic molecular theory?

A) 0°C
B) -100°C
C) -273.15°C
D) 273.15°C

View Answer

41. The ideal gas law applies best under which conditions?

A) High temperature and low pressure
B) Low temperature and high pressure
C) Low temperature and low pressure
D) High temperature and high pressure

View Answer

42. Which of the following gases is considered the most ideal in behavior?

A) Oxygen
B) Nitrogen
C) Helium
D) Water vapor

View Answer

43. The unit of the gas constant “R” in the ideal gas equation is:

A) atm L/mol K
B) atm/mol K
C) L/mol K
D) K/mol

View Answer

44. According to Boyle’s law, if a gas occupies 10 L at 2 atm pressure, what will be its volume at 4 atm?

A) 20 L
B) 10 L
C) 5 L
D) 2.5 L

View Answer

45. If the volume of a gas increases, what happens to the pressure, assuming constant temperature?

A) Increases
B) Decreases
C) Remains constant
D) Doubles

View Answer

46. The concept of absolute zero is important because at absolute zero:

A) The volume of a gas becomes infinite
B) All molecular motion stops
C) The pressure of a gas increases
D) The temperature of a gas is doubled

View Answer

47. The general gas equation can be used to calculate changes in which variables?

A) Only pressure and temperature
B) Only volume and temperature
C) Pressure, volume, and temperature
D) Pressure and mass

View Answer

48. According to the kinetic molecular theory, gas particles move in:

A) Circular paths
B) Straight-line paths
C) Zigzag paths
D) Rotational motion

View Answer

49. If the temperature of a gas is increased, its kinetic energy:

A) Decreases
B) Increases
C) Remains the same
D) Doubles

View Answer

50. What is the relationship between pressure and temperature at constant volume according to Gay-Lussac’s law?

A) P ∝ V
B) P ∝ 1/T
C) P ∝ T
D) P ∝ n

View Answer

51. In the ideal gas equation, what is the unit of volume?

A) Cubic meters
B) Liters
C) Kilograms
D) Joules

View Answer

52. A gas at 300 K has a volume of 5 L. What will be its volume if the temperature is increased to 600 K, assuming constant pressure?

A) 2.5 L
B) 10 L
C) 7.5 L
D) 20 L

View Answer

53. The concept of partial pressure is based on which law?

A) Boyle’s law
B) Charles’s law
C) Dalton’s law
D) Graham’s law

View Answer

54. Which gas law best explains the working of a hot air balloon?

A) Boyle’s law
B) Charles’s law
C) Graham’s law
D) Avogadro’s law

View Answer

55. What happens to the speed of gas molecules as the temperature increases?

A) Increases
B) Decreases
C) Remains constant
D) Doubles

View Answer

56. At constant temperature, if the pressure of a gas increases, the volume will:

A) Increase
B) Decrease
C) Remain the same
D) Triple

View Answer

57. The term “kinetic” in the kinetic molecular theory refers to:

A) Volume
B) Speed
C) Energy
D) Pressure

View Answer

58. Which law relates the number of moles of a gas to its volume at constant temperature and pressure?

A) Boyle’s law
B) Avogadro’s law
C) Dalton’s law
D) Gay-Lussac’s law

View Answer

59. The pressure exerted by a gas is a result of:

A) The mass of the gas particles
B) The volume of the gas
C) The collisions of gas particles with the walls of the container
D) The attractive forces between gas particles

View Answer

60. What is the ideal gas law equation?

A) P = nRT/V
B) PV = nRT
C) P = RT/nV
D) PV = R/T

View Answer

61. Which of the following gases would have the highest average kinetic energy at the same temperature?

A) Nitrogen
B) Oxygen
C) Helium
D) Carbon dioxide

View Answer

62. Boyle’s law holds true when the temperature of a gas is:

A) Constant
B) Increasing
C) Decreasing
D) Zero

View Answer

63. Which law relates pressure and temperature at constant volume?

A) Charles’s law
B) Boyle’s law
C) Gay-Lussac’s law
D) Dalton’s law

View Answer

64. What will happen to the volume of a gas if its temperature is decreased to 1/3 of its original value at constant pressure?

A) The volume will triple
B) The volume will become 1/3
C) The volume will remain the same
D) The volume will decrease to 1/2

View Answer

65. The ideal gas equation assumes that gas particles:

A) Have no volume
B) Have a fixed volume
C) Attract each other
D) Move in circular paths

View Answer

66. According to Graham’s law, the rate of effusion of a gas is inversely proportional to:

A) Its temperature
B) Its molar mass
C) Its volume
D) Its pressure

View Answer

67. In the context of gases, absolute zero refers to:

A) The point at which molecular motion stops
B) The highest temperature possible
C) The point where pressure equals volume
D) The boiling point of water

View Answer

68. The volume of a gas at 0°C is 10 L. What will its volume be at 100°C, assuming constant pressure?

A) 20 L
B) 15 L
C) 5 L
D) 30 L

View Answer

69. If the number of gas molecules in a container is doubled, what will happen to the pressure, assuming constant temperature and volume?

A) It will double
B) It will decrease by half
C) It will remain the same
D) It will quadruple

View Answer

70. The volume of a gas is directly proportional to the number of moles at constant temperature and pressure according to:

A) Boyle’s law
B) Charles’s law
C) Avogadro’s law
D) Dalton’s law

View Answer

71. According to the kinetic molecular theory, the average speed of gas molecules increases with:

A) Increasing pressure
B) Increasing volume
C) Increasing temperature
D) Decreasing temperature

View Answer

72. The pressure of a gas is measured in which unit?

A) Liters
B) Moles
C) Atmospheres
D) Celsius

View Answer

73. The combined gas law is expressed as:

A) PV = nRT
B) P₁V₁/T₁ = P₂V₂/T₂
C) V₁/T₁ = V₂/T₂
D) P₁V₁ = P₂V₂

View Answer

74. The relationship between pressure and volume of a gas at constant temperature is described by:

A) Charles’s law
B) Boyle’s law
C) Avogadro’s law
D) Gay-Lussac’s law

View Answer

75. In the ideal gas equation, “n” represents:

A) Number of molecules
B) Number of moles
C) Mass of the gas
D) Volume of the gas

View Answer

76. The Kelvin scale is used in gas calculations because it starts at:

A) Absolute zero
B) Standard temperature
C) Room temperature
D) Freezing point of water

View Answer

77. If 1 mole of an ideal gas occupies 22.4 L at STP, what will be the volume occupied by 2 moles?

A) 22.4 L
B) 44.8 L
C) 11.2 L
D) 5.6 L

View Answer

78. Which of the following assumptions is NOT part of the kinetic molecular theory?

A) Gas particles are in constant random motion.
B) Gas particles have a significant volume compared to their container.
C) Gas particles collide elastically.
D) There are no attractive forces between gas particles.

View Answer

79. In a rigid container, increasing the temperature of a gas will result in:

A) Increased volume
B) Increased pressure
C) Decreased pressure
D) No change in pressure

View Answer

80. A gas occupies a volume of 3.0 L at a pressure of 2.0 atm. What will be its pressure if the volume is decreased to 1.5 L at constant temperature?

A) 1.0 atm
B) 4.0 atm
C) 3.0 atm
D) 2.5 atm

View Answer

81. The assumption that gas particles do not attract or repel each other is made in which law?

A) Boyle’s law
B) Charles’s law
C) Ideal gas law
D) Graham’s law

View Answer

82. The speed of gas molecules is affected by which of the following factors?

A) Mass of the molecules
B) Pressure of the gas
C) Volume of the gas
D) Temperature of the gas

View Answer

83. What is the relationship between volume and temperature at constant pressure called?

A) Avogadro’s law
B) Boyle’s law
C) Charles’s law
D) Graham’s law

View Answer

84. At standard temperature and pressure (STP), the volume of one mole of any gas is approximately:

A) 22.4 L
B) 10.0 L
C) 24.0 L
D) 32.0 L

View Answer

85. Which gas law would you use to calculate the change in pressure of a gas when its volume is decreased while temperature is held constant?

A) Avogadro’s law
B) Charles’s law
C) Gay-Lussac’s law
D) Boyle’s law

View Answer

86. In an isothermal process, which variable remains constant?

A) Volume
B) Temperature
C) Pressure
D) Moles

View Answer

87. Which of the following is a characteristic property of gases?

A) Definite shape
B) Definite volume
C) Compressibility
D) High density

View Answer

88. Which of the following conditions most favors real gases to behave ideally?

A) High temperature and low pressure
B) Low temperature and high pressure
C) High pressure and low temperature
D) High pressure and high temperature

View Answer

89. In a gas, the average distance between particles is:

A) Very small
B) Small
C) Moderate
D) Very large

View Answer

90. What happens to the pressure of a gas when its temperature is increased at constant volume?

A) Increases
B) Decreases
C) Remains the same
D) Becomes zero

View Answer

91. When gas molecules collide with the walls of a container, this collision contributes to the:

A) Volume of the gas
B) Pressure of the gas
C) Temperature of the gas
D) Density of the gas

View Answer

92. In the ideal gas law, if the pressure is doubled while the volume remains constant, what will happen to the temperature?

A) It will double
B) It will remain the same
C) It will be halved
D) It will triple

View Answer

93. What is the primary factor that causes gas particles to behave differently at high pressures?

A) Increased volume
B) Intermolecular forces
C) Increased temperature
D) Decreased kinetic energy

View Answer

94. If a gas has a molar mass of 44 g/mol, and its rate of effusion is compared to a gas with a molar mass of 22 g/mol, how do the rates compare?

A) The heavier gas effuses faster
B) The lighter gas effuses faster
C) Both gases effuse at the same rate
D) Cannot be determined

View Answer

95. A gas occupies a volume of 10 L at a pressure of 1 atm. What will be its volume at 2 atm, assuming constant temperature?

A) 20 L
B) 5 L
C) 10 L
D) 15 L

View Answer

96. The ideal gas law assumes that gas molecules have:

A) A small volume and no intermolecular forces
B) Significant volume and strong intermolecular forces
C) A large volume and weak intermolecular forces
D) A moderate volume and moderate intermolecular forces

View Answer

97. What is the relationship between pressure and volume in a gas at constant temperature known as?

A) Charles’s law
B) Avogadro’s law
C) Boyle’s law
D) Dalton’s law

View Answer

98. What effect does increasing the temperature of a gas have on its pressure at constant volume?

A) It increases pressure.
B) It decreases pressure.
C) It has no effect on pressure.
D) It causes pressure to drop significantly.

View Answer

99. Which statement is true regarding real gases compared to ideal gases?

A) Real gases have no volume.
B) Real gases experience intermolecular forces.
C) Real gases behave perfectly at all conditions.
D) Real gases do not have kinetic energy.

View Answer

100. According to the ideal gas law, what happens to the volume of a gas if its number of moles is increased while pressure and temperature remain constant?

A) The volume decreases.
B) The volume increases.
C) The volume remains the same.
D) The volume becomes zero.

View Answer