Which law, that was proposed in 1811, predicted that the same volume of gases at the same temperature and pressure would have the same number of molecules?

Avogadro's law

The correct answer is option 2. Avogadro's law.

The law that predicts that the same volume of gases at the same temperature and pressure would have the same number of molecules is Avogadro's law. It was proposed in 1811 by Amedeo Avogadro.

• Dalton's law: This law states that the total pressure of a mixture of ideal gases is equal to the sum of the partial pressures of each individual gas in the mixture. It doesn't relate to the number of molecules in a specific volume.
• Gay-Lussac's law: This law states that for a fixed amount of gas at constant pressure, the volume is directly proportional to the absolute temperature. It doesn't directly relate the volume of gases to the number of molecules.
• Charles's law: This law states that for a fixed amount of gas at constant volume, the pressure is directly proportional to the absolute temperature. It doesn't directly relate the volume of gases to the number of molecules.

Therefore, only Avogadro's law specifically addresses the relationship between the volume of gases, temperature, pressure, and the number of molecules.