7-4 Avogadro’s Principle (Section 13.4 ) And you!

Avogadro’s Principle states that for a gas at constant temperature and pressure, the volume is directly proportional to the number of moles of gas. In equation form: Volume = constant x moles orV = constant x n

Rearranging gives us: V 1 = constant = V 2 or V 1 = V 2 n 1 n 2 n 1 n 2 Another way to interpret this principle is: equal volumes of different gases (at constant T and P) have the same number of molecules.

7-5 The Ideal Gas Law (Section 13.5) It’s possible to combine all the gas laws we’ve learned into one expression called the Ideal Gas Law: PV = nRT P = pressure V = volume (in L) n = number of mole T = temperature (in K) R = the Universal Gas Constant = Latm= 8.31 LkPa = 62.4 LmmHg molK molK molK All the gas laws can be derived from the Ideal Gas Law; for example, by holding V and n constant.

The Ideal Gas Law can be used to calculate additional quantities other than P, V, and T: Using the idea that the molar mass (formula weight) = grams/mole or MM = grams/n Sub in gives: PV = gRT MM which can be used to find MM !!!!! Rearrange for Density: g/V = Density of gas = g/V = P(MM) / RT