Question

The temperature of a monatomic ideal gas remains constant during a process in which 4500 J of heat flows out of the gas. How much work (including the proper + or - sign) is done on the gas?
J

Answer 1

Well, to start - You must compress the gas to get heat out at constant temperature --> work in

The process is isothermal (constant temp)

In an ideal gas, the internal energy U depends only on T, so the change in U is zero so
0 = Q - W
but Q = -4500 J
so
0 = -4500 + W
W = +4500 = work done BY gas
so -4500 is work done ON the gas

Answer 2

I'm not sure what we are doing wrong but the computer is saying -4500 is wrong

Answer 3

so
0 = -4500 - W ======= NOT + W
W = -4500 = work done BY gas
so +4500 is work done ON the gas

I prefaced this whole thing by telling you why W had to be positive then did not notice my sign error.