# Effect on Volume of a Change in the Pressure of Compressible Gas

Summary:
From 12.4 MPa and 5660 L in pressurized cylinder to 500KPa will Volume available increase?
Will the available Volume of oxygen gas for use of patients increase when the pressure decreases from 12.4 MPa to 500 KPa?
Is using boyle's law the right way to calculate the available volume?

## Answers and Replies

berkeman
Mentor
Welcome to the PF.

Is this question for schoolwork? If so, we can move it to the Homework Help forums where schoolwork is posted.

Also, what other constraints are there on this change in pressure? Is it isothermal? Other than Boyle's Law, is there another more detailed Law that could also apply?

rjomega
Baluncore
Science Advisor
Will the available Volume of oxygen gas for use of patients increase when the pressure decreases from 12.4 MPa to 500 KPa?
If the pressure is reduced the volume will increase.

Is the 5660 litre you quote the volume of oxygen gas at atmospheric pressure, that has then been stored in a smaller ( ≈45.5 litre) portable cylinder at 12.4 MPa, or is 5660 litre the volume of a big high pressure storage cylinder that is about 6 metres long ?

Why 500 kPa ? That is five atmospheres. Unless the patient is in a hyperbaric chamber the patient will breath oxygen at 1 atmosphere pressure. If distributed within a hospital at 5 atm, the pressure will be reduced to 100 kPa where it is administered to the patient.

The important thing is the total mass of oxygen available. That is independent of the pressure and volume used to store or distribute the gas to patients. Efficient expansion is not important for medical oxygen delivery.

rjomega and berkeman