The volume of a gas is 0.250 L at 340.0 kPa pressure. What will the volume be when the pressure is reduced to 50.0 kPa, assuming the temperature remains constant?
The good thing about Boyle's law is that here, given the proportionality, we don't have to bother about converting units; we could use pints, and bushels, and pounds and shillings and pence if we liked.
Clearly volume will INCREASE almost sevenfold, as we would expect if we reduce the pressure.
The final volume of this gas will be 1.7L.
Assuming this is an ideal gas, and that the number of molecules *n of this gas remains *constant, and given that the temperature is also constant, we have then a situation where the Boyle-Mariotte Law** applies.
This law basically states that pressure P and volume V of a gas are inversely proportional when the number of molecules and temperature are constant:
That is, in these conditions, pressure times volume is constant :
So if we compare two separate situations, we conclude that
Now we can solve this problem. We know that the initial pressure is
If we cancel out the pressure units, we end up with a volume unit, which is precisely what we want:
So the final volume of this gas, at 50kPa, will be:
This is in accordance with Boyle-Mariotte, which implies that an increase in pressure results in a decrease in volume, and vice-versa.
Hope this helped!