1. The problem statement, all variables and given/known data A hand pump of volume 2.0 x 10-4 m3 is used to force air through a valve into a container of volume 8.0 x 10-4 m3 which contains air at an initial pressure of 101kPa. Calculate the pressure of the air in the container after one stroke of the pump, assuming the temperature if unchanged. 2. The attempt at a solution Firstly bear in mind that this is the first question of the Gases section in my A2 physics textbook, so I have a hunch that this question should be quite simple, as well as the fact that only Boyle's law has been covered so far in this section. So anyway, I assume that Boyle's law is involved: PV = k (where P = pressure, V = volume, k = constant). I started by fiinding the constant by subbing in the initial pressure (of the container) and its volume to get constant k = 80.8 I then subbed the constant value I've just found, and the volume of 8.0 x 10-4 m3 minus 2.0 x 10-4 m3 into the same PV = k equation. I figured that if air is being pumped in, then the container's volume must be reduced as the pumped in air takes up space, hence why I put volume as: 8.0 x 10-4 m3 minus 2.0 x 10-4 m3. However I get pressure as 134kPa. The answer at the back have it as 126kPa.