MediumChemistryHigh School (11–12)Chemical Thermodynamics › Systems, Work, Heat and the First LawNumericalConceptual
A gas in an insulated cylinder is compressed by 450 J of work.
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
A gas in an insulated cylinder is compressed by J of work. (a) Find . (b) The same gas, from the same start, is brought to the same final state in a rigid container, by heating alone. How much heat is needed? (c) In a third trial, J of work is done on the gas. How much heat must it give out to reach the same final state?
Need a reminder? The key ideaShow
First law: . Energy into the system is positive: for heat absorbed, for work done on the system. Adiabatic change: , so . For a whole cycle, .
The worked solution
Have you tried it?
Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.
Step 1. Adiabatic. , so J.
Step 2. Heating alone. A rigid container means no work: J.
Step 3. The third trial. is still J, so J. The gas must give out J of heat.
Answer: J; J of heat; J.
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