A #4 L# container holds #19 # mol and #20 # mol of gasses A and B, respectively. Groups of four of molecules of gas B bind to three molecule of gas A and the reaction changes the temperature from #210^oK# to #120^oK#. How much does the pressure change?
I'll answer a question for a fellow Wisconsinite!
The trickiest part of this problem is determining the change in the number of moles from the reaction.
We are given all the information we need to calculate the initial pressure if we make the assumption that gasses A and B are ideal. (In reality this is not often the case at 120K!)
When the two types of gasses react, they form a new gas C. The problem states that the reaction goes as follows:
We know that the limiting reagent here is gas B since we require 33% more B than A for the reaction yet we only have about 5% more B than A before the reaction. We will assume that this reaction goes to completion so that there is no gas B after the reaction.
Because of the reaction stoichiometry
The total number of moles of gas after the reaction,
Again assuming the ideal gas law holds we can calculate the pressure after the reaction.