Stella,
I assumed that you have had calculus.
If you have not, then your book must say something like:
For an ideal gas:
With compression at constant temperature,
work in = (n R T) ln (V1/V2)
or
With compression at constant temperature
heat out = (n R T) ln (V1/V2)
Since change in internal energy = heat in - work out
and internal energy depends only on temperature
your work in is the same as the heat out
You are given the work in, so you have :
work in
n, number of moles
R gas constant
V1 and V2
so you can calculate T
Three moles of an ideal gas are compressed from 5.5*10^-2 to 2.5*10^-2 m^3. During the compression, 6.1*10^3J of work is done on the gas, and heat is removed to keep the temperature of the gas constant at all times. Find the temperature of the gas.
I posted this question few hours ago, and someone gave me such hints to do it. However, I don't quite get it, can anyone please explain more about it?THANKS A LOT!
p V = n R T is state equation before and after
Now work done at constant temp
dW = -p dV
but p = (n R T)/V and here n R T is constant given
so
dW = -(nRT) dV/V
so
work done = (nRT) ln(V1/V2)
by the way, that is also the heat out since internal energy depends only on T which is constant.
4 answers
work in = (n R T) ln (V1/V2)
what is the "1n" standing for?
what is the "1n" standing for?
ln is natural log. Log to the base e. It is on your calculator, probably on the same key as e^x
This must be in your physics book. Look in the index for isothermal compression or expansion or simply compression or expansion. It may be in a paragraph on "work done during volume changes".
0 answers