Gases and Gas Laws MCQs 2026

Boyle's law states that at constant temperature, the volume of a fixed mass of gas is

1. A Inversely proportional to its pressure ✓
2. B Directly proportional to its pressure ✓
3. C Independent of pressure ✓
4. D Directly proportional to the square of pressure ✓

Charles's law states that at constant pressure, the volume of a fixed mass of gas is

1. A Directly proportional to its absolute temperature ✓
2. B Inversely proportional to its absolute temperature ✓
3. C Independent of temperature ✓
4. D Inversely proportional to the square of temperature ✓

Gay-Lussac's law states that at constant volume, the pressure of a fixed mass of gas is

1. A Inversely proportional to temperature ✓
2. B Independent of temperature ✓
3. C Inversely proportional to volume ✓
4. D Directly proportional to its absolute temperature ✓

The ideal gas equation is expressed as

1. A PV = nRT/2 ✓
2. B P/V = nRT ✓
3. C PT = nRV ✓
4. D PV = nRT ✓

In the ideal gas equation PV=nRT, R represents the

1. A Avogadro's number ✓
2. B Universal gas constant ✓
3. C Rate constant ✓
4. D Refractive index ✓

Standard temperature and pressure (STP) conditions are

1. A 100°C and 2 atm ✓
2. B 25°C and 1 atm ✓
3. C 0°C and 2 atm ✓
4. D 0°C (273 K) and 1 atm ✓

At STP, 1 mole of an ideal gas occupies a volume of

1. A 24.0 L ✓
2. B 20.0 L ✓
3. C 22.4 L ✓
4. D 11.2 L ✓

Avogadro's law states that equal volumes of gases at the same temperature and pressure contain

1. A Equal masses ✓
2. B Equal densities ✓
3. C Different numbers of molecules ✓
4. D Equal numbers of molecules ✓

Dalton's law of partial pressures applies to

1. A A single pure gas only ✓
2. B A mixture of non-reacting gases ✓
3. C Liquids only ✓
4. D Solids only ✓

According to Dalton's law, the total pressure of a gas mixture equals the

1. A Sum of the partial pressures of each gas ✓
2. B Product of partial pressures ✓
3. C Average of partial pressures ✓
4. D Difference of partial pressures ✓

Graham's law of diffusion states that the rate of diffusion of a gas is inversely proportional to the

1. A Pressure of the gas ✓
2. B Temperature of the gas ✓
3. C Square root of its molar mass ✓
4. D Volume of the container ✓

According to kinetic molecular theory, gas particles are considered to be in

1. A Fixed positions ✓
2. B Rest at low temperature only ✓
3. C Constant, random motion ✓
4. D Motion only when heated above 100°C ✓

Kinetic molecular theory assumes that collisions between gas molecules are

1. A Inelastic ✓
2. B Perfectly elastic ✓
3. C Always attractive ✓
4. D Never occurring ✓

The kinetic energy of gas molecules is directly proportional to the

1. A Pressure of the gas ✓
2. B Volume of the container ✓
3. C Absolute temperature ✓
4. D Molar mass ✓

Real gases deviate from ideal behavior most significantly at

1. A High temperature and low pressure ✓
2. B High pressure and low temperature ✓
3. C Low pressure and high temperature ✓
4. D Standard conditions only ✓

Real gases deviate from the ideal gas law mainly because ideal gas theory ignores

1. A Temperature effects ✓
2. B The universal gas constant ✓
3. C Intermolecular forces and the volume of gas particles ✓
4. D Avogadro's number ✓

The van der Waals equation modifies the ideal gas equation to account for

1. A Intermolecular forces and molecular volume ✓
2. B Temperature changes only ✓
3. C Avogadro's number ✓
4. D Partial pressures ✓

According to Boyle's law, if the pressure of a gas is doubled at constant temperature, its volume will

1. A Double ✓
2. B Be halved ✓
3. C Remain the same ✓
4. D Quadruple ✓

If the absolute temperature of a fixed mass of gas is doubled at constant pressure, its volume will

1. A Remain the same ✓
2. B Double ✓
3. C Be halved ✓
4. D Quadruple ✓

Absolute zero temperature is

1. A 0°C ✓
2. B -273.15°C ✓
3. C -100°C ✓
4. D 100 K ✓

At absolute zero, according to kinetic theory, the kinetic energy of gas molecules is theoretically

1. A Zero ✓
2. B Maximum ✓
3. C Infinite ✓
4. D Equal to room temperature value ✓

The combined gas law relates pressure, volume, and temperature as

1. A PV/T = constant only if n changes ✓
2. B P1V1T1 = P2V2T2 ✓
3. C P1V1/T1 = P2V2/T2 ✓
4. D PT/V = constant ✓

Which gas law explains why a balloon shrinks when placed in liquid nitrogen

1. A Charles's law ✓
2. B Boyle's law ✓
3. C Graham's law ✓
4. D Dalton's law ✓

Which gas would diffuse fastest under identical conditions

1. A Hydrogen ✓
2. B Oxygen ✓
3. C Carbon dioxide ✓
4. D Chlorine ✓

The compressibility factor (Z) for an ideal gas is always equal to

1. A 0 ✓
2. B Infinity ✓
3. C Less than 1 ✓
4. D 1 ✓

Which of the following gases would be expected to behave most ideally

1. A Ammonia ✓
2. B Water vapor ✓
3. C Helium ✓
4. D Sulfur dioxide ✓

The pressure exerted by a gas is due to

1. A Collisions of gas molecules with the walls of the container ✓
2. B Gravity acting on gas molecules ✓
3. C Chemical bonds between molecules ✓
4. D Loss of electrons by molecules ✓

Vapor pressure of a liquid increases with

1. A Decreasing temperature ✓
2. B Increasing intermolecular forces ✓
3. C Decreasing surface area ✓
4. D Increasing temperature ✓

A gas is said to be at its critical temperature when

1. A It cannot be liquefied by pressure alone above this temperature ✓
2. B It becomes a solid ✓
3. C Its volume becomes zero ✓
4. D Its pressure becomes infinite ✓

The value of the universal gas constant R in SI units is approximately

1. A 0.0821 L·atm/(mol·K) only ✓
2. B 8.314 J/(mol·K) ✓
3. C 22.4 J/(mol·K) ✓
4. D 6.022 J/(mol·K) ✓

Which of the following conditions favors ideal gas behavior

1. A High pressure, low temperature ✓
2. B Low temperature, high pressure ✓
3. C Both high pressure and low temperature ✓
4. D Low pressure, high temperature ✓

The molar volume of any ideal gas at STP is the same because of

1. A Graham's law ✓
2. B Boyle's law ✓
3. C Avogadro's law ✓
4. D Dalton's law ✓

Which gas law is used to determine the molar mass of a gas from its rate of diffusion relative to another gas

1. A Boyle's law ✓
2. B Charles's law ✓
3. C Graham's law ✓
4. D Gay-Lussac's law ✓

As temperature increases, the average kinetic energy of gas molecules

1. A Decreases ✓
2. B Remains constant ✓
3. C Increases ✓
4. D Becomes zero ✓

According to kinetic theory, the volume occupied by gas molecules themselves is assumed to be

1. A Equal to the container's volume ✓
2. B Significant compared to container volume ✓
3. C Half the container volume ✓
4. D Negligible compared to the container's volume ✓

Which of these gases would deviate most from ideal behavior at high pressure

1. A Helium ✓
2. B Hydrogen ✓
3. C Neon ✓
4. D Ammonia ✓

The pressure of a gas sample is measured using a

1. A Thermometer ✓
2. B Hydrometer ✓
3. C Calorimeter ✓
4. D Manometer/Barometer ✓

At constant temperature and pressure, the volume of a gas is directly proportional to the

1. A Molar mass ✓
2. B Density ✓
3. C Number of moles (Avogadro's law) ✓
4. D Square root of pressure ✓

A gas that obeys PV = nRT exactly under all conditions of temperature and pressure is called a/an

1. A Real gas ✓
2. B Ideal gas ✓
3. C Noble gas ✓
4. D Diatomic gas ✓

Which of the following is true for an isothermal process involving a gas

1. A Temperature changes but volume constant ✓
2. B Temperature remains constant ✓
3. C Pressure remains constant ✓
4. D Volume remains constant ✓

1 atmosphere of pressure is equal to

1. A 76 mm Hg ✓
2. B 100 kPa exactly ✓
3. C 1 mm Hg ✓
4. D 760 mm Hg ✓

Which scientist's name is associated with the law relating volume and number of moles of gas

1. A Avogadro ✓
2. B Boyle ✓
3. C Charles ✓
4. D Dalton ✓

The density of an ideal gas at constant temperature and pressure is directly proportional to its

1. A Volume ✓
2. B Universal gas constant ✓
3. C Temperature ✓
4. D Molar mass ✓

Which of the following best explains why gases can be compressed much more easily than liquids

1. A Gas molecules are heavier ✓
2. B There is a lot of empty space between gas molecules ✓
3. C Gas molecules attract each other strongly ✓
4. D Gas molecules have higher density ✓

The SI unit of pressure is the

1. A Pascal ✓
2. B Newton ✓
3. C Joule ✓
4. D Atmosphere ✓

As altitude increases, atmospheric pressure

1. A Increases ✓
2. B Decreases ✓
3. C Remains constant ✓
4. D Becomes negative ✓

Which gas law would explain why a sealed bag of chips expands at higher altitude

1. A Charles's law ✓
2. B Graham's law ✓
3. C Gay-Lussac's law ✓
4. D Boyle's law ✓

The mean free path of gas molecules is the average distance travelled between

1. A Successive collisions ✓
2. B Boiling and condensation ✓
3. C Ionization events ✓
4. D Nucleus and electron ✓

Effusion refers to the escape of gas molecules through

1. A A tiny opening into a vacuum or lower-pressure region ✓
2. B A solid membrane impermeable to gas ✓
3. C A liquid solution ✓
4. D Chemical reaction only ✓

According to Graham's law, if gas A diffuses twice as fast as gas B, then the molar mass of B is ___ that of A

1. A Half ✓
2. B Equal to ✓
3. C Four times ✓
4. D Twice ✓