# change in entropy at constant temperature

by ricof
Tags: constant, entropy, temperature
 P: 14 1. The problem statement, all variables and given/known data Calculate the entropy change when 0.011m3 of a perfect gas at a constant temperature of 273K is compressed from an initial pressure 1x10^5 N/m/m to a pressure of 1x10^6 N/m/m. I know the equation but cannot work out Q!! Please help! 2. Relevant equations dS=Q/T 3. The attempt at a solution
 PF Patron HW Helper Sci Advisor P: 2,532 Hi ricof, welcome to PF. Can you combine the First Law with what you know about the energy of an ideal gas at constant temperature?
 P: 29 Some more relevant equations. The first law $$\Delta E=Q+W$$ Work for isothermal expansion $$W=-nRTln\frac{V_{f}}{V_{i}}$$ If you combine this with what you know about change in internal energy at constant temperature, like Mapes said, and that integral of yours, you can figure out the answer.
P: 14

## change in entropy at constant temperature

Because T is constant, there is no change in internal energy right?

And also, in the above equation for isothermal expansion, how is n calculated?
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