Which proportionality correctly describes Avogadro's law?

• A. Volume is directly proportional to temperature (V ∝ T) at constant pressure and number of moles.
• B. Volume is directly proportional to the number of moles of gas (V ∝ n) at constant temperature and pressure.
• C. Volume is inversely proportional to pressure (V ∝ 1/P) at constant temperature and number of moles.
• D. Pressure is directly proportional to temperature (P ∝ T) at constant volume and number of moles.

Answer: (B)

Verified step by step guidance

1. Recall that Avogadro's law states the relationship between the volume of a gas and the amount of gas (in moles) when temperature and pressure are held constant.
2. Express Avogadro's law mathematically as \(V \propto n\) when temperature (\(T\)) and pressure (\(P\)) are constant.
3. Understand that this means if you increase the number of moles of gas while keeping temperature and pressure constant, the volume increases proportionally.
4. Note that other proportionalities mentioned relate to different gas laws: for example, \(V \propto T\) at constant pressure and moles is Charles's law, \(V \propto \frac{1}{P}\) at constant temperature and moles is Boyle's law, and \(P \propto T\) at constant volume and moles is Gay-Lussac's law.
5. Therefore, the correct proportionality for Avogadro's law is volume directly proportional to the number of moles, \(V \propto n\), at constant temperature and pressure.