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QPages 76-77: Q13: HC Verma: Concepts of Physics - Volume 2 Specific Heat Capacities of Gases Pages 76-77: Q13 Solution: The molar heat capacity of oxygen gas at STP is nearly 2.5 R.…

⚠️ Common Exam Traps & Conceptual Pitfalls

Students often mistake the gradual rise of $C$ from $2.5R$ to $3.5R$ as evidence that O$_2$ is dissociating into atoms, but the temperatures involved are far below the dissociation threshold. The correct explanation is that vibrational modes of the O$_2$ molecule become thermally excited, adding $R$ per active vibrational degree of freedom. Avoid conflating dissociation with vibrational activation when interpreting heat‑capacity data.

The molar heat capacity of oxygen gas at STP is nearly 2.5 R. As the temperature is increased, it gradually increases and approaches 3.5 R. The most appropriate reason for this behaviour is that at high temperatures

Multiple Choice Options

  • A oxygen does not behave as an ideal gas
  • B oxygen molecules dissociate in atoms
  • C the molecules collide more frequently
  • D molecular vibrations gradually become effective

Step-by-Step Verified Solution

**Answer:** (d) molecular vibrations gradually become effective. **Step-by-Step Explanation:** At high temperatures, vibrational modes of the oxygen molecule become active, increasing C_v from 2.5R towards 3.5R.

All Questions in this Chapter

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