Gases and Gas Laws MCQs 2026

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

1. AInversely proportional to its pressure✓
2. BDirectly proportional to its pressure✓
3. CIndependent of pressure✓
4. DDirectly proportional to the square of pressure✓

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

1. ADirectly proportional to its absolute temperature✓
2. BInversely proportional to its absolute temperature✓
3. CIndependent of temperature✓
4. DInversely 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. AInversely proportional to temperature✓
2. BIndependent of temperature✓
3. CInversely proportional to volume✓
4. DDirectly proportional to its absolute temperature✓

The ideal gas equation is expressed as

1. APV = nRT/2✓
2. BP/V = nRT✓
3. CPT = nRV✓
4. DPV = nRT✓

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

1. AAvogadro's number✓
2. BUniversal gas constant✓
3. CRate constant✓
4. DRefractive index✓

Standard temperature and pressure (STP) conditions are

1. A100°C and 2 atm✓
2. B25°C and 1 atm✓
3. C0°C and 2 atm✓
4. D0°C (273 K) and 1 atm✓

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

1. A24.0 L✓
2. B20.0 L✓
3. C22.4 L✓
4. D11.2 L✓

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

1. AEqual masses✓
2. BEqual densities✓
3. CDifferent numbers of molecules✓
4. DEqual numbers of molecules✓

Dalton's law of partial pressures applies to

1. AA single pure gas only✓
2. BA mixture of non-reacting gases✓
3. CLiquids only✓
4. DSolids only✓

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

1. ASum of the partial pressures of each gas✓
2. BProduct of partial pressures✓
3. CAverage of partial pressures✓
4. DDifference of partial pressures✓

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

1. APressure of the gas✓
2. BTemperature of the gas✓
3. CSquare root of its molar mass✓
4. DVolume of the container✓

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

1. AFixed positions✓
2. BRest at low temperature only✓
3. CConstant, random motion✓
4. DMotion only when heated above 100°C✓

Kinetic molecular theory assumes that collisions between gas molecules are

1. AInelastic✓
2. BPerfectly elastic✓
3. CAlways attractive✓
4. DNever occurring✓

The kinetic energy of gas molecules is directly proportional to the

1. APressure of the gas✓
2. BVolume of the container✓
3. CAbsolute temperature✓
4. DMolar mass✓

Real gases deviate from ideal behavior most significantly at

1. AHigh temperature and low pressure✓
2. BHigh pressure and low temperature✓
3. CLow pressure and high temperature✓
4. DStandard conditions only✓

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

1. ATemperature effects✓
2. BThe universal gas constant✓
3. CIntermolecular forces and the volume of gas particles✓
4. DAvogadro's number✓

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

1. AIntermolecular forces and molecular volume✓
2. BTemperature changes only✓
3. CAvogadro's number✓
4. DPartial pressures✓

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

1. ADouble✓
2. BBe halved✓
3. CRemain the same✓
4. DQuadruple✓

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

1. ARemain the same✓
2. BDouble✓
3. CBe halved✓
4. DQuadruple✓

Absolute zero temperature is

1. A0°C✓
2. B-273.15°C✓
3. C-100°C✓
4. D100 K✓

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

1. AZero✓
2. BMaximum✓
3. CInfinite✓
4. DEqual to room temperature value✓

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

1. APV/T = constant only if n changes✓
2. BP1V1T1 = P2V2T2✓
3. CP1V1/T1 = P2V2/T2✓
4. DPT/V = constant✓

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

1. ACharles's law✓
2. BBoyle's law✓
3. CGraham's law✓
4. DDalton's law✓

Which gas would diffuse fastest under identical conditions

1. AHydrogen✓
2. BOxygen✓
3. CCarbon dioxide✓
4. DChlorine✓

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

1. A0✓
2. BInfinity✓
3. CLess than 1✓
4. D1✓

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

1. AAmmonia✓
2. BWater vapor✓
3. CHelium✓
4. DSulfur dioxide✓

The pressure exerted by a gas is due to

1. ACollisions of gas molecules with the walls of the container✓
2. BGravity acting on gas molecules✓
3. CChemical bonds between molecules✓
4. DLoss of electrons by molecules✓

Vapor pressure of a liquid increases with

1. ADecreasing temperature✓
2. BIncreasing intermolecular forces✓
3. CDecreasing surface area✓
4. DIncreasing temperature✓

A gas is said to be at its critical temperature when

1. AIt cannot be liquefied by pressure alone above this temperature✓
2. BIt becomes a solid✓
3. CIts volume becomes zero✓
4. DIts pressure becomes infinite✓

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

1. A0.0821 L·atm/(mol·K) only✓
2. B8.314 J/(mol·K)✓
3. C22.4 J/(mol·K)✓
4. D6.022 J/(mol·K)✓

Which of the following conditions favors ideal gas behavior

1. AHigh pressure, low temperature✓
2. BLow temperature, high pressure✓
3. CBoth high pressure and low temperature✓
4. DLow pressure, high temperature✓

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

1. AGraham's law✓
2. BBoyle's law✓
3. CAvogadro's law✓
4. DDalton'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. ABoyle's law✓
2. BCharles's law✓
3. CGraham's law✓
4. DGay-Lussac's law✓

As temperature increases, the average kinetic energy of gas molecules

1. ADecreases✓
2. BRemains constant✓
3. CIncreases✓
4. DBecomes zero✓

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

1. AEqual to the container's volume✓
2. BSignificant compared to container volume✓
3. CHalf the container volume✓
4. DNegligible compared to the container's volume✓

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

1. AHelium✓
2. BHydrogen✓
3. CNeon✓
4. DAmmonia✓

The pressure of a gas sample is measured using a

1. AThermometer✓
2. BHydrometer✓
3. CCalorimeter✓
4. DManometer/Barometer✓

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

1. AMolar mass✓
2. BDensity✓
3. CNumber of moles (Avogadro's law)✓
4. DSquare root of pressure✓

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

1. AReal gas✓
2. BIdeal gas✓
3. CNoble gas✓
4. DDiatomic gas✓

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

1. ATemperature changes but volume constant✓
2. BTemperature remains constant✓
3. CPressure remains constant✓
4. DVolume remains constant✓

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

1. AAvogadro✓
2. BBoyle✓
3. CCharles✓
4. DDalton✓

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

1. AVolume✓
2. BUniversal gas constant✓
3. CTemperature✓
4. DMolar mass✓

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

1. AGas molecules are heavier✓
2. BThere is a lot of empty space between gas molecules✓
3. CGas molecules attract each other strongly✓
4. DGas molecules have higher density✓

The SI unit of pressure is the

1. APascal✓
2. BNewton✓
3. CJoule✓
4. DAtmosphere✓

As altitude increases, atmospheric pressure

1. AIncreases✓
2. BDecreases✓
3. CRemains constant✓
4. DBecomes negative✓

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

1. ACharles's law✓
2. BGraham's law✓
3. CGay-Lussac's law✓
4. DBoyle's law✓

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

1. ASuccessive collisions✓
2. BBoiling and condensation✓
3. CIonization events✓
4. DNucleus and electron✓

Effusion refers to the escape of gas molecules through

1. AA tiny opening into a vacuum or lower-pressure region✓
2. BA solid membrane impermeable to gas✓
3. CA liquid solution✓
4. DChemical 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. AHalf✓
2. BEqual to✓
3. CFour times✓
4. DTwice✓