Which statement best describes Gay-Lussac's law?

• A. The total pressure of a mixture of gases is equal to the sum of the partial pressures of each gas.
• B. The pressure of a fixed amount of gas is directly proportional to its absolute temperature at constant volume.
• C. The pressure of a fixed amount of gas is inversely proportional to its volume at constant temperature.
• D. The volume of a fixed amount of gas is directly proportional to its absolute temperature at constant pressure.

Answer: (B)

Verified step by step guidance

1. Identify that Gay-Lussac's law relates the pressure and temperature of a gas when the amount of gas and volume are held constant.
2. Recall the mathematical form of Gay-Lussac's law: \(P \propto T\) at constant volume and amount of gas, which can be written as \(\frac{P_1}{T_1} = \frac{P_2}{T_2}\), where \(P\) is pressure and \(T\) is absolute temperature in Kelvin.
3. Understand that this means pressure increases linearly with temperature if volume and moles of gas do not change.
4. Compare this with other gas laws: Dalton's law relates total pressure to partial pressures, Boyle's law relates pressure and volume inversely at constant temperature, and Charles's law relates volume and temperature at constant pressure.
5. Conclude that the statement 'The pressure of a fixed amount of gas is directly proportional to its absolute temperature at constant volume' best describes Gay-Lussac's law.