| While the properties of gasses may not seem at first to be important to the tudy of chemistry, it is actually fundamental. The earliest scientific experiments that established the atomic theory, such as Lavoisers's Lwa of Conservation of Mass and Dalton's Law of Multiple Proportions, commonly employed gaseos compounds. The use of gases was helpful, in part, because of gaseos compounds are usually simple and demonstrate the atomic nature of matter easier than complicated compounds.
Avagadro's Law is the simple gas law that directly expresses the atomic, or molecular nature of a gas. His law states that the volume of gas is proportional to the number of moles of a gas molecule, regardless of the chemical composition. This means that any sample of a gas at a certain volume, pressure and temperature will have the same number of moles as another sample that has the same volume, pressure, and temperature even if the two samples contain entirely different compounds. Thus, the volume, pressure, and temperature measurements of a gas sample provide a direct direct measurement of the number of moles of molecules without even knowing the chemical formula. In reactions involving gases one can use Avogadro's Law to track moles of product gases as they form and moles of reactant gases asd they are used up; a technique used by John Dalton in developling the Law of Multiple Proportions. In this experiment you will test Avogadro's Law by measuring the number of molecules in 45.0 mL samples of four different gases: nitrogen (N2), Oxygen (O2), propane (C3H8), and butane (C4H10) at room temperature and pressure. We will assume, however, we do not yet know the Ideal Gas Law, so the number of molecules will be determined by measuring the mass of the gas and using molar mass and Avogadro's number. In the end, if Avogadro's Law is ture then the number of gas molecules in each 45.0 mL sample should be the same (within experimental error). From the average number of molecules of gas in the 45.0 mL you will finnally test to see if your results also agree with the Ideal Gas Law by calculating the volume occupied by 1 mole of your gases at STP and comparing it to the Ideal Gas Law value of 22.4 L. |
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