Which statement best describes Gay-Lussac's law?

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

Answer: (A)

Verified step by step guidance

1. Identify that Gay-Lussac's law relates the pressure and temperature of a gas when the volume and amount of gas are held constant.
2. Recall the mathematical expression of Gay-Lussac's law: \(P \propto T\) at constant volume, 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 if the temperature of a gas increases, its pressure increases proportionally, provided the volume does not change.
4. Compare this with other gas laws: Charles's law relates volume and temperature at constant pressure, Dalton's law relates total pressure to partial pressures, and Boyle's law relates volume and pressure at constant temperature.
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.