A sealed rigid container holds a gas at 1.0 atm and 27 °C. What is its pressure when heated to 327 °C?
Correct answer A. 2.0 atm
Topic / 40 questions
Gases MCQs
Gases MCQs are multiple-choice questions on the gas laws, the ideal gas equation, the kinetic molecular theory and the behaviour of real gases. They match the MDCAT chemistry curriculum, and every question on MCQs360 shows its correct answer instantly, so you can practise numerical and conceptual questions with immediate feedback.
- Gases 40
- Liquids 40
- Solids 40
- Chemical Equilibrium 40
- Reaction Kinetics 40
- Thermochemistry and Energetics 40
- Electrochemistry 40
- Fundamental Concepts of Chemistry 40
- Atomic Structure 39
- Chemical Bonding 39
- Alcohols and Phenols 38
- Industrial Chemistry 37
- Aldehydes and Ketones 37
- Alkyl Halides 37
- s- and p-Block Elements 37
- Chemistry of Hydrocarbons 36
- Fundamental Principles of Organic Chemistry 36
- Carboxylic Acids 36
- Transition Elements 35
- Macromolecules 35
According to the kinetic molecular theory, how do gas molecules move?
Correct answer A. Randomly in straight lines until they collide
For a fixed mass of gas at constant temperature, which plot gives a straight line passing through the origin?
Correct answer A. P against 1/V
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Which expression represents Charles’s law for a fixed mass of gas at constant pressure?
Correct answer D. V/T = constant
How do Boyle’s law isotherms (P against V curves) change as the temperature of the gas is raised?
Correct answer C. They move further away from the axes
A gas at 0 °C is heated at constant pressure until its volume doubles. What is its final temperature?
Correct answer A. 273 °C
0.64 g of a gas occupies 224 cm³ at STP. What is its molar mass?
Correct answer B. 64 g mol⁻¹
What is the density of carbon dioxide at STP (C = 12, O = 16; molar volume = 22.4 dm³)?
Correct answer A. 1.96 g dm⁻³
About how many molecules are present in 1 cm³ of an ideal gas at STP?
Correct answer C. 2.69 × 10¹⁹
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In the van der Waals equation, the constant b is related to ____
Correct answer D. the actual volume occupied by the gas molecules
Which gas is expected to show the greatest deviation from ideal behaviour at room temperature?
Correct answer C. NH₃
For a real gas at moderate pressure, the compressibility factor Z is less than 1. What does this indicate?
Correct answer A. Attractive forces between molecules dominate
At the same temperature, how does the average kinetic energy of H₂ molecules compare with that of O₂ molecules?
Correct answer A. It is the same
Using average kinetic energy = (3/2)RT per mole, what is the translational kinetic energy of 1 mol of gas at 300 K (R = 8.314 J K⁻¹ mol⁻¹)?
Correct answer B. 3.74 kJ
Why are gases much more compressible than liquids and solids?
Correct answer A. There are large empty spaces between gas molecules
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According to the kinetic molecular theory, the pressure of a gas is caused by ____
Correct answer D. collisions of molecules with the walls of the container
For a fixed mass of an ideal gas at constant temperature, how does the product PV vary as pressure increases?
Correct answer C. It remains constant
From the ideal gas equation, how does the density of a gas change?
Correct answer B. It increases with pressure and decreases with temperature
A gas occupies 2.0 dm³ at 1.0 atm and 273 K. What is its volume at 2.0 atm and 546 K?
Correct answer D. 2.0 dm³
What is −73 °C expressed on the Kelvin scale?
Correct answer C. 200 K
About Gases MCQs
The numerical questions apply Boyle's law and Charles's law to changes in pressure, volume and temperature, convert between Celsius and Kelvin, and use the ideal gas equation PV = nRT with the correct value and units of R. Pressure conversions between atm, mm Hg and kPa also appear, so learn the standard values at STP. The conceptual questions test the postulates of the kinetic molecular theory: elastic collisions, negligible molecular volume and an average kinetic energy proportional to absolute temperature. Further questions ask about absolute zero, the conditions under which real gases deviate most from ideal behaviour and the two corrections made in the van der Waals equation.
Key facts to remember
- Boyle's law: at constant temperature, the volume of a fixed mass of gas is inversely proportional to its pressure (PV = constant).
- Charles's law: at constant pressure, volume is directly proportional to absolute temperature; the volume changes by 1/273 of its 0 °C value for each 1 °C change.
- At STP (0 °C and 1 atm, or 760 mm Hg) one mole of an ideal gas occupies 22.4 dm³.
- The general gas constant R = 8.314 J K⁻¹ mol⁻¹ = 0.0821 dm³ atm K⁻¹ mol⁻¹.
- Absolute zero is 0 K, or −273.15 °C, and T(K) = t(°C) + 273.
- Real gases deviate most from ideal behaviour at high pressure and low temperature; the van der Waals equation is (P + an²/V²)(V − nb) = nRT.
Exams that include Gases MCQs
Pakistan
- MDCAT
- ECAT
- NUMS
- AKU
- FSc boards
India
- NEET
- JEE Main
Bangladesh
- HSC
- Medical Admission Test
How to prepare for Gases MCQs
- Always convert temperatures to kelvin before using any gas law.
- Learn R in both SI units and dm³ atm units, and pick the value that matches the units in the question.
- Remember what each van der Waals constant corrects: a for intermolecular attraction and b for molecular volume.
- Write the kinetic theory postulates as a short list and revise them alongside the reasons real gases deviate.
Frequently asked questions
What does the MDCAT syllabus include in Gases?
The PMDC MDCAT curriculum for Gases covers the postulates of the kinetic molecular theory, STP values, Boyle's law and Charles's law, absolute zero, the ideal gas equation with the units of R, and the differences between real and ideal gases.
Which exams ask Gases MCQs?
Gas laws and kinetic theory are tested in MDCAT, ECAT, NUMS and AKU entry tests and in FSc board exams in Pakistan. In India, NEET and JEE Main test ideal gases and kinetic theory, and in Bangladesh the topic appears in HSC and medical admission tests.
Why do real gases deviate from ideal behaviour?
Real gas molecules have a finite volume and attract one another, while the ideal gas model assumes neither. These effects matter most at high pressure, when molecules are crowded together, and at low temperature, when they move slowly enough for attractions to take effect.
Last reviewed October 2026