A Level Chemistry OCR Practice Exam

What does the Boltzmann distribution represent?

1. The movement of electrons in an atom

2. The distribution of energies at a specific temperature

3. The total number of molecules in a system

4. The ratio of gases in a mixture

The correct answer is: The distribution of energies at a specific temperature

The Boltzmann distribution represents the distribution of energies at a specific temperature. This statistical distribution describes how energy is shared among the molecules of a gas or other system at thermal equilibrium. At a given temperature, molecules will have a range of kinetic energies, and the Boltzmann distribution illustrates the likelihood of finding molecules with different energy levels. At higher temperatures, the distribution broadens, indicating that a greater proportion of molecules have higher energies, whilst at lower temperatures, the distribution is narrower and most molecules have lower energies. This concept is key in understanding various phenomena, such as reaction rates and thermodynamic properties, because the energy distribution influences how molecules collide and react with one another. The movement of electrons in an atom is described by quantum mechanics and is not directly represented by the Boltzmann distribution. The total number of molecules in a system is a simple count and does not convey the energy distribution among those molecules. Lastly, the ratio of gases in a mixture relates to Dalton's law of partial pressures and does not pertain to energy distribution. Thus, recognizing the significance of the Boltzmann distribution in reflecting the energies at a specific temperature highlights why this choice is correct.