Work Done By Gases - Calculating Pressure, Volume & Heat

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In a closed container with a piston, when heat is added to a gas, the volume increases while the pressure remains constant. The work done by the gas can be calculated using the formula W = P * ΔV, where ΔV is the change in volume. In this scenario, the change in volume is 40 - 15, resulting in a positive value for ΔV. Despite initial confusion, the correct interpretation is that the work done is equivalent to the energy added, which is 1200 J, in this isobaric process. Therefore, W = 1200 J is the accurate conclusion for this situation.
Timothy Schablin
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Consider a gas in a closed container with a piston allowed to move. Let's start with a volume of 15 and pressure of 1.5. We add heat to the system, let's say 1200 J. This forces the piston to move increasing the volume to 40. The pressure remains the same, 1.5. When calculating the work done by the gas, how do we go about it?

W = P * change in Volume.

So, since the pressure remains constant, do we just take change in volume, 15 - 40 = -25?
Or 1.5(15-40)?
Or add in the heat to the system? (15-40) + 1200?
 
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Timothy Schablin said:
do we just take change in volume, 15 - 40 = -25?
Volume increases. Change of volume is ΔV=40-15 (you did not say the unit).

Timothy Schablin said:
W = P * change in Volume.

So, since the pressure remains constant, do we just take change in volume, 15 - 40 = -25?
Or 1.5(15-40)?
W=p*ΔV not W=Δp*ΔV
 
apparently, the correct answer is the amount of energy added, or 1200J. This is an isobaric situation so I guess W=PV doesn't work?

All my research on the 'net points to W=PV though...
 
Timothy Schablin said:
apparently, the correct answer is the amount of energy added, or 1200J. This is an isobaric situation so I guess W=PV doesn't work?
What is the exact wording of the question and the analysis that led to this result?
All my research on the 'net points to W=PV though...
Then I guess you have more research to do. Do you have an actual thermodynamics book?
 
Timothy Schablin said:
apparently, the correct answer is the amount of energy added, or 1200J. This is an isobaric situation so I guess W=PV doesn't work?

All my research on the 'net points to W=PV though...
correct is ##W=p \cdot _\Delta V##
 

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