# Thermodynamics - Carnot cycle

1. Mar 22, 2014

### Feodalherren

1. The problem statement, all variables and given/known data
An ideal gas is taken through a Carnot cycle. The
isothermal expansion occurs at 250°C, and the isothermal
compression takes place at 50.0°C. The gas takes in 1 200 J
of energy from the hot reservoir during the isothermal
expansion. Find (a) the energy expelled to the cold reservoir
in each cycle and (b) the net work done by the gas in
each cycle.

2. Relevant equations

3. The attempt at a solution

Qh=1200J.

Qh-W=Qc (absolute values)

e(Carnot)=(523-323)/523= 61.9 %
(corrected my typo from before)

Therefore Qc= .381(1200J)=457J

and W = 1200-457=743J

Not the correct answer. Qc = 741 according to the solutions manual.

ps. Latex seems to be bugged, didn't work in "preview post" mode.

Last edited: Mar 22, 2014
2. Mar 22, 2014

### TSny

Hello. Check this calculation.

3. Mar 22, 2014

### Feodalherren

Hi there.

Woops I typed it in wrong, it was supposed to be (523-323)/523= .619

The answer is still incorrect though.

4. Mar 22, 2014

### SteamKing

Staff Emeritus
That's not the problem. Check the numbers. Remember, you are looking for a difference of 2 joules.

5. Mar 22, 2014

### Feodalherren

Give me another hint, please. I still don't know what I'm doing wrong :). Is my logic even sound?

6. Mar 22, 2014

### TSny

e = (523-323)/523 is correct. But this does not equal .619

7. Mar 22, 2014

### Feodalherren

what?! How did I miss that, I re-did it like 3 times :/. Thank you though.

8. Mar 22, 2014

### TSny

Also, to get the anwer of 741 J it appears that you should convert to Kelvin by adding 273.15 rather than 273.