Equal volumes of two different gases are held at the same temperature and the same pressure. What do the two samples have in common?

1. Avogadro's law compares gas samples held at the same temperature and pressure. 2. Equal volumes of gases under those conditions contain the same number of molecules. 3. Nothing in the law refers to the mass of the samples. 4. Different gases have different molar masses, so equal numbers of molecules give unequal masses. 5. Different molecules also contain different numbers of atoms each, so the atom counts differ too. 6. Choosing the same mass is the common trap, because it quietly assumes every gas weighs the same per molecule. _Source: Siyavula Physical Sciences Grade 11 (Everything Science, CC BY 4.0), Chapter 7: Ideal gases_