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Avogadro's hypothesis states that equal volumes of all gases, at the same temperature and pressure, have the same number of molecules. The law of combining volumes states that the volumes of reacting gases, and the volumes of the gaseous products, are in small whole-number ratios when measured at the same temperature and pressure. To explain the law of combining volumes using Avogadro's hypothesis, we remember that the number of molecules in equal volumes of gases at the same temperature and pressure is the same, regardless of the gas type. Therefore, if two gases react in a specific volume ratio, the same number ratio applies for their molecules. This number ratio represents the small whole numbers mentioned in the law of combining volumes. Thus, Avogadro's hypothesis helps explain the law of combining volumes in terms of molecule numbers.

In this case, we have a 1.0-L flask containing neon gas and a 1.5-L flask containing xenon gas. Both gases are at the same pressure and temperature. According to Avogadro's law, the number of atoms in these flasks can be compared. Since the volume of the neon gas flask is 1.0 L and the volume of the xenon gas flask is 1.5 L, we can set up the following ratio, using the relationship of Avogadro's hypothesis (the number of atoms is directly proportional to the volume of gas, for the same temperature and pressure): Ratio of atoms (Ne:Xe) = Volume ratio (Ne:xenon) = 1.0 L / 1.5 L

To calculate the ratio of atoms between the neon gas and xenon gas, we simply divide 1.0 L by 1.5 L: Ratio of atoms (Ne:Xe) = 1.0 L / 1.5 L = 2/3 So, according to Avogadro's law, the ratio of the number of neon atoms to the number of xenon atoms in the two flasks is 2:3.