The Quantity-Volume Relationship Avogadros Law

The relationship between the quantity of a gas and its volume follows from the work of Joseph Louis Gay-Lussac (1778-1823) and Amedeo Avogadro (1776-1856). 

Three years later Amedeo Avogadro interpreted Gay-Lussac s observation by proposing what is now known as Avogadro s hypothesis Equal volumes of gases at the same temperature and pressure contain equal numbers of molecules. For example, 22.4 L of any gas at 0 °C and 1 atm contain 6.02 X 10 gas molecules (that is, 1 mol), as depicted inT FIGURE 10.10. 

Avogadro s law follows from Avogadro s hypothesis The volume of a gas maintained at constant temperature and pressure is direcdy proportional to the number of moles of the gas. That is, 

Suppose we have a gas confined to a cylinder with a movable piston. (Sections 5.2,5.3) Consider the following changes (assuming no leaks) (a) Heat the gas from 298 K to 360 K at constant pressure, (b) Reduce the volume from I L to 0.5 L at constant temperature, (c) Inject additional gas, keeping temperature and volume constant. Indicate how each change affects the average distance between molecules, the pressure of the gas, and the number of moles of gas in the cylinder. 

Analyze We need to think how each change affects (I) the distance between molecules, (2) the pressure of the gas, and (3) the number of moles of s in the cylinder. 

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