Worked Example

checklist
Mark Yourself Question
  1. Grab a piece of paper and try this problem yourself.
  2. When you're done, check the "I have answered this question" box below.
  3. View the solution and report whether you got it right or wrong.
Four moles of an ideal gas originally at 323 oC and 7.3 atm underwent a complete expansion against a constant external pressure of 1 atm and did 8kJ of work. Calculate q, ΔE, ΔH.

Solve for the missing initial variable (Vi):
hint: rearrange PV=nRT to do this!
Solve for Vf:
Hint: We can use Vi and the work to find Vf
In the work equation, recall P must be in Pa!
We now have three of four final variables. We can solve for Tf
With the initial and final temperatures we can find ΔH and ΔU
Recall: Cp= 5/2(R)
Cv=3/2(R) You should know this for your exam!
To find the total heat flow we need to use ΔU,
More First Law of Thermodynamics Questions:
More Ideal Gas Law Questions: