Which of the following correctly states Gay-Lussac's law?

• A. The pressure of a fixed amount of gas is inversely proportional to its volume at constant temperature.
• B. The volume of a fixed amount of gas is inversely proportional to its pressure at constant temperature.
• C. The volume of a fixed amount of gas is directly proportional to its absolute temperature at constant pressure.
• D. The pressure of a fixed amount of gas is directly proportional to its absolute temperature at constant volume.

Answer: (D)

Verified step by step guidance

1. Understand that Gay-Lussac's law describes the relationship between the pressure and temperature of a fixed amount of gas when the volume is held constant.
2. Recall that according to Gay-Lussac's law, pressure (\(P\)) is directly proportional to the absolute temperature (\(T\)) when volume (\(V\)) and amount of gas are constant.
3. Express this relationship mathematically as \(P \propto T\) or \(\frac{P}{T} = k\), where \(k\) is a constant for a given amount of gas at constant volume.
4. Recognize that this means if the temperature increases, the pressure increases proportionally, and if the temperature decreases, the pressure decreases proportionally, as long as volume does not change.
5. Compare the given options and identify the statement that matches this direct proportionality between pressure and absolute temperature at constant volume as the correct expression of Gay-Lussac's law.