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First Law of Thermodynamics and ideal gas

  • #1

Homework Statement


An ideal gas expands isothermally, performing 3.40x10^3 J of work in the process.
a) The change in internal energy of the gas
b) The heat absorbed during this expansion


Homework Equations


[tex]\Delta[/tex]U=Q-W


The Attempt at a Solution


a) Since it's isothermally expanding, there will be no change in internal temperature, so:
[tex]\Delta[/tex]U=0

b) Q=W, so:
Q=-3400 J
 

Answers and Replies

  • #2
Mapes
Science Advisor
Homework Helper
Gold Member
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17
Looks good, as long as positive heat means that the system is heating the environment and positive work means that the environment is doing work on the system. This sign convention is a little unconventional, though.
 
  • #3
Doc Al
Mentor
44,882
1,129
b) Q=W, so:
Good.
Q=-3400 J
How did that negative sign sneak in? (W is positive, so Q is positive.)
 
  • #4
Ah, ok. That was a silly mistake, lol :)

So Q=3400 J
 

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