Work done BY the system is negative.
Here is the way to remember it.
You know delta H is + when heat is absorbed (receiving) and - when the heat is emitted(giving).
Work is + when receiving) and - when giving.
A gas absorbs 45 kJ of heat and does 29 kJ of work. Calculate the change in energy.
The answer is 16 kJ, but I don't understand why.
If a gas absorbs heat and does 29 kJ of work. Wouldn't they both be positive?
Change in energy = q + w
45 kJ + 29 kJ = 74 kJ
Why is the work negative?
Thanks.
4 answers
Ahhh, that's really helpful. Thanks for clearing it up.
This is wrong it should be 16 kJ as you subtract 45-29 which equals 16.
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