# If #2/5# #L# of a gas at room temperature exerts a pressure of #15# #kPa# on its container, what pressure will the gas exert if the container's volume changes to #7/3# #L#?

##### 1 Answer

Before starting the calculation, it's worth thinking about what we expect the answer to be. We have the same amount of gas, in a container that is getting a lot bigger: from

With the same amount of gas in a larger container, we expect the pressure to be lower than the initial

There are a number of possible approaches to doing the calculation. My own favourite way is to use the Combined Gas Law and then remove the one that we're not using:

In this case, we are not changing temperatures, so we can remove that:

Rearranging to make

Now we can substitute in the values from the question: