What is the work done on the gas for path IAF using a P-V graph?

[alexithymia916]

Homework Statement

One mole of gas is initially at a pressure of 3.9 atm, volume of .29 L and has an internal energy equal to 108.1 J. In its final state the gas is at pressure 1 atm and volume .7 L, and its internal energy equals 169 J. (There are 6 different questions using this data).

For the path IAF, calculate the work done on the gas. Answer in units of J

okay well there is a graph to better visualize the problem but i can't exactly draw it out but basically the path IAF makes a right angle (If you start from point I you go down and then right). I is at 3.9 atm and .29 L, A is at 1 atm and .29 L, and F is at 1 atm and .7 L.

Homework Equations

Work = Pressure x Change in Volume

The Attempt at a Solution

Well to start it off, there is no work done from I to A so therefore you only need to find the work from point A to F
W from path A to F= (1 atm)(.41 litres)
convertingggg
W=(101300 N/m^2)(.00041 m^3)
so you should get
41.533 N*m
so
41.533 J

and somehow when i submit that in, it comes at as wrong... help?

 

[Andrew Mason]

For the path IAF, calculate the work done on the gas. Answer in units of J

It is asking for the work done ON the gas. Is the gas doing work or is work being done on it here?

AM

 

[alexithymia916]

okay so if it's work being done on the gas.. then the equation should be
Change in Internal energy = Q-W
but you don't have specific heat or final or initial temperature..

 

[Andrew Mason]

okay so if it's work being done on the gas.. then the equation should be
Change in Internal energy = Q-W
but you don't have specific heat or final or initial temperature..

When gas expands, it DOES work. So in this case, it DOES work, so the work DONE ON the gas is negative. Just put a - sign in front of your answer.

AM

 

[alexithymia916]

oh geeeez
pardon my ignorance...
thanks so much :)