Homework Help: Non-ideal Gas: Withdrawing gas from bottle with increasing temperature

1. Sep 10, 2007

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1. The problem statement, all variables and given/known data
A gas mixture (80.1 mol% CO2, 12.2 mol% CO and balance Ar) is stored in a gas bottle. The volume of the gas bottle is 317.0 liters. Initially the pressure of the gas in the bottle is 14.2 MPa and the temperature is 25.3 °C

Qn: The gas is being withdrawn from the bottle at a constant rate of 310.2 moles/hour. As this is occurring the temperature of the gas in the bottle is increasing at a rate of 13.7 °C/hr. How long does it take for the pressure of the gas in the bottle to reach 3.0 MPa?

2. Relevant equations
Non-ideal gas equation: PV = znRT

3. The attempt at a solution
I tried doing this by calculating the pressure of the gas in the bottle every one hour. Since the temperature is increasing, the pressure will constantly be changing every moment. Next i plotted a graph of pressure of gas vs time and joined the dots. i could locate the 3.0 MPa point but i think it's not accurate enough. Can anyone help out please? Thanks!