IB A15.1 PV Diagrams and Work
Get the Formative Assessment: FA15.1.docx
How to solve the Formative Assessment:
This is a Pressure v Volume graph for 0.280 mols of an ideal gas.
The system starts at a pressure of 175. Pa and a volume of 1.60 m3 and goes through these four processes:
Isobaric (constant pressure) compression to 0.400 m3
Isochoric (constant volume) cooling to 50.0 Pa
Isobaric expansion to 1.60 m3
Isochoric heating to 175 Pa
Draw all four processes. Use arrows for the processes, and label each process 1, 2, 3 or 4
1. Calculate the highest and lowest temperature (in K) Label these temperatures at the corners on the graph above.
(8.60 K and 120. K)
2. Calculate the work done by each process, and the net work done by the gas in the entire cycle.
(1: -210 J, 2: 0, 3: + 60. J, 4: 0 Net work = -150 J)
Problems like this:
Single processes:
Complete cycles:
3. At what temperature in Celsius does 14.0 grams of Helium have a total internal energy of 9450 J?
(He = 4.003 g/mol)
(-56.4 oC)
4A&B.
4A. 32 J of heat flow into a gas, and its internal energy drops by 17 J, how much work did the gas do? Does the temperature rise or fall? (Answer both questions)
(+49 J of work, temp falls)
4B. Fred does 35 J of work compressing a gas in a cylinder, and the internal energy rises by 13 J, what is the amount of heat flow into the gas? Does heat flow into or out of the gas? (Answer both questions)
(-22 J, heat flowed out)
Problems like this: (These proved to be vexing when they were on the test - I would do all of them on the 15 worksheet I gave you)
5. What is the change in entropy of 1.20 kg of water boiling into vapor at 100.0 oC? (L = 22.6x105 J/kg)
(+7270 J/K)
The Instruction for this unit:
