An #8 L# container holds #5 # mol and #9 # mol of gasses A and B, respectively. Every two molecules of gas B bind to one molecule of gas A and the reaction raises the temperature from #320^oK# to #450 ^oK#. How much does the pressure change by?
The key to this problem is to find the number of moles of gas before and after the reaction.
We can then use the ideal gas equation to find the pressure in each case and hence the pressure change.
Before the gases react we have a total number of moles of 5 + 9 = 14.
We can write the equation as:
This tells us that 1 mole of
So 9 moles of
This means that there must be an excess 0.5 moles of
So the total moles of gas after reaction = 0.5 + 4.5 = 5.
The ideal gas equation gives us :
(note I have converted
So you can see that the pressure has dropped by
Although the temperature has increased this is more than offset by the decrease in the number of particles brought about by the reaction, hence the reduction in pressure.