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#molecular physics

3 public questions tagged with this topic.

Internal Energy of Ideal Gases

How many degrees of freedom does a diatomic molecule have if its vibrational mode is active?

**Ideal gas internal energy** proportional to temperature, U = (f/2) R T per mole, monatomic 3/2 R T, diatomic 5/2 R T, change ΔU = f/2 n R ΔT, for temperature increase internal energy rises, explaining why heating gas at constant volume raises U entirely as heat. Diatomic molecule: 3 translational + 2 rotational + 1 vibrational (2 modes: KE and PE).Total degrees of freedom = 3 + 2 + 2 = 7. Substituting values gives 7, which matches expected kinetic theory result, confirming mean free path λ = 1/(√2 n π d²), ideal gas law P V = n R T and v_rms = √(3 R T/M) relations.

Ref: NCERT > Physics Book > Behaviour of Perfect Gas and Kinetic Theory > Internal Energy of Ideal Gases

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Chemical Bonding

What happens to Van der Waals interactions when two molecules get too close?

They turn repulsive correctly describes the effect or change asked about in this question. In Chemical Bonding, understanding cause-and-effect relationships is essential for predicting biological outcomes. They turn repulsive occurs because of specific molecular interactions, thermodynamic principles, or regulatory mechanisms that govern this biological process. The other options (They become stronger, They remain unchanged, and They turn into hydrogen bonds) describe either opposite effects, effects that occur under different conditions, or changes associated with unrelated processes.

Ref: Campbell Biology, Urry et al., 12th Ed.

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Chemical Bonding

Which of the following correctly describes the London dispersion force?

Can be attractive or repulsive is the scientifically accurate answer to this question. Within the study of Chemical Bonding, this concept is well-established through extensive research and is documented in standard scientific literature. The specific properties, mechanisms, or characteristics of Can be attractive or repulsive directly address what is being asked. Among the other options, Exists only in polar molecules, Stronger than hydrogen bonding, and Requires high dielectric constant do not correctly answer this question because they either refer to different concepts, describe properties

Ref: Campbell Biology, Urry et al., 12th Ed.

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