A Levels Chemistry (9701)•9701/11/M/J/21
Explanation
Ideal gas behavior depends on weak intermolecular forces and small molecular size
Steps:
- Ideal gases assume point particles with no attractions or repulsions.
- Real gases deviate more if polar or large, increasing intermolecular forces.
- Under room conditions (25°C, 1 atm), compare boiling points and polarity as indicators of ideality.
- Helium has the lowest boiling point (-269°C) and is monatomic/nonpolar, minimizing deviations.
Why A is correct:
- Helium's monatomic structure and extremely weak van der Waals forces align closest with the ideal gas law PV = nRT, showing minimal deviations in compressibility factors.
Why the others are wrong:
- B. Nitrogen: Diatomic molecule with moderate van der Waals forces, causing slight deviations compared to helium.
- C. Ammonia: Polar with hydrogen bonding, leading to strong attractions and significant non-ideal behavior.
- D. Krypton: Larger noble gas with higher polarizability and boiling point (-153°C), resulting in more intermolecular interactions.
Final answer: A
Topic: States of matter
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