# PV=nRT Question

## Homework Statement

A standard cylinder of oxygen used in a hospital has gauge pressure = 2.0E3 psi (1.38E4 kPa) and
volume = 16 L (0.016 m3) at T = 295 K. How long will the cylinder last if the flow rate, measured at atmospheric pressure, is
constant at 1.8 L/min?

## Homework Equations

PV=nRT
n=m/M
flowrate=volume/time

## The Attempt at a Solution

I assume it's not as simple as 16/1.8?

I used PV=(m/M)RT to solve for mass, but that got me no where.

Dick
Homework Helper
The gas in the cylinder is under pressure. So it is equivalent to many more liters at atomospheric pressure. Find out how many and then it is as simple as you think.

The gas in the cylinder is under pressure. So it is equivalent to many more liters at atomospheric pressure. Find out how many and then it is as simple as you think.

So nRT is constant correct?

So (PV)_inside=(PV)_outside?

(1.38*10^4kPa)(.016m^3)=(P_atmosphere)(V)

Solve for V, then use that in t=V/flowrate?

Thanks,
Brandon

you may have to use calculus to solve this

you may have to use calculus to solve this

No, it's the lowest level physics class.

Dick