Tn = C
The temperature(Kelvin) and the number of moles (n) are inversely related if the volume and pressure are held constant. Picture an iron box containing n moles of a gas. Imagine you then increased the temperature inside the box. Remember that temperature is a measure of the average kinetic energy, or energy of motion. Therefore, when energy is added to these gas molecules, they will move at an increased speed. Increased speed results in increased number of collisions (Just imagine a set number of people in a closed room moving randomly and without stopping. There will be more numbers of collisions among them if they run than if they walk). This increase in the number of collisions would in turn increase the pressure. Therefore, if the pressure is to be held constant, the number of moles must decrease to reduce the number of collisions when the temperature is increased. Thus, the temperature and the number of moles (n) are inversely related if the volume and pressure are held constant. If X=T and Y=n, and three of the four variables are known, then setting up an equation such as X1Y1=X2Y2 is a good way to algebraically solve problems involving a Tn=C relationship.
Sample Questions
1. A container held 1.3 moles of methane at 25'C. How many moles will it hold if the temperature increased to 75'C and the pressure remains constant?
2. A container at an initial temperature of 0'C holds 3.5 moles of chlorine gas. If the number of moles was decreased to 0.5, what is the highest temperature that can be reached without changing the pressure..
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PV = C V/n = C P/n = C V/T = C
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