I’m hoping someone can help me understand this concept.
So according to Boyle’s Law, pressure and volume are indirectly proportional
P1V1=P2V2
With that in mind when pressure goes up, volume goes down. Why does the opposite happen when you are decreasing pressure in an Oxygen tank?
I’m thinking it has to do with the release of the gas but is there a different formula that calculates the remaining volume when you are decreasing the PSI on the gauge?
Or am I using the equation incorrectly.
In: Physics
That relationship only holds when no gas enters or leaves the system. An oxygen tank is a fixed volume, so if the pressure gauge reading goes down some of the oxygen is leaving.
You can however say that if the pressure has gone down by a certain percentage , the total number of molecules of gas has reduced by that factor, ie. that your cylinder has lost that percentage of its contents. That is using the Ideal Gas Equation PV = nRT where n is the number of moles of gas and R is the gas constant (8.314 J /K.mole)
Not sure I understand your question, but…
In a cylinder, the volume is fixed (i.e. the cylinder isn’t getting any larger/smaller); however the volume that the gas takes up changes under pressure.
Avagadro’s constant – 1 mole of gas takes up 22.4dm3 of volume at standard temperature & pressure. If you take 1 mole of gas and change increase the pressure, then it will take up less space.
Imagine the volume of your cylinder is 22.4L. Fill it with an uncompressed gas, and you’ll end up with 1 mole of it; compress it and you have more gas in there.
You are thinking of it incorrectly. Boyle’s law is best explain when using a cylinder as an example.
As you push on the rod of cylinder you are decreasing the volume in the cylinder and increasing the pressure because the gas is being compressed; when you pull the rod out you are increasing the volume and decreasing the pressure because you are decompressing the gas.
Edit: If you are asking because of SCUBA reason just remember the deeper you go under water the more pressure the water is applying to you thus the more you and your equipment are being compressed and this is why Boyle’s law applies here.
It may help to think of it the other way around. As volume goes down, pressure goes up with a set amount of gas. You’re trying to stuff the same amount of gas into a smaller container, so pressure would increase. Going the other way, if you have a larger container, there is more room for gas to pressure is lower. That doesn’t mean you have less gas, just that there is more space.
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