Here is a pic of the question. The question is easy to solve but I need to assume constant pressure to do so. It doesn't mention in the question whether pressure is constant however. But in other questions in the same assignment, pressure is constant. So should it be safe to assume constant pressure or is there a solution I don't see? (Unlikely)

Question

anonymous · Answer

http://tinypic.com/r/2qinsd0/8 The pic can be found at the above link

anonymous · Answer

@Abhisar  @paki  @wio

abhisar · Answer

Where is the question?

anonymous · Answer

It's in the picture

anonymous · Answer

Question picture link is posted above.

anonymous · Answer

@Nnesha @aaronq @zepdrix

anonymous · Answer

@texaschic101  @Abhisar

anonymous · Answer

@hartnn

anonymous · Answer

@Loser66

anonymous · Answer

Guys any help/suggestions would be great. I just need some help with making this assumption. The problem itself is easy.

michele_laino · Answer

I think that the pressure is constant

michele_laino · Answer

pressure of nitrogen, of course

anonymous · Answer

Yeah that's what I wanted to assume as well. This is problem 3, in problem 4 they tell you to take the pressure as constant. That's why I was wondering if it would be a safe assumption. Once I can assume that, all is well.

michele_laino · Answer

from your picture, I can see that the nitrogen gas makes a free expansion, namely the only pressure against nitrogen is the external pressure, which is constant I think

anonymous · Answer

The atmospheric pressure I believe is neglected here and isn't of concern. It's just the heat that is expanding the gas. Since the temperature is increasing, and the temperature is increasing the volume, then it should imply that pressure remains constant.

michele_laino · Answer

more precisely, I think that the constant pressure has to be considered as an initial hypothesis. Afterthat, if we apply the equation of state ofgases, we can write this:
$$\Large  {T_{final}} = 2{T_{initial}}$$

michele_laino · Answer

work $W$ done by nitrogen gas, is:
$$W = {P_1}\left( {{V_2} - {V_1}} \right) = {P_1}\left( {2{V_1} - {V_1}} \right) = {P_1}{V_1}$$
where $P_\,V_$ are initial pressure and volume of nitrogen, respectively

michele_laino · Answer

oops...
where $P_1,V_1$ are initial pressure and volume of nitrogen, respectively

anonymous · Answer

Yeah all that is trivial. The problem is trivial. The only issue I had was the original assumption. Not looking for a solution, just the help whether I should assume that or not. From what I've read now and what you are saying, that should be the right assumption.

michele_laino · Answer

ok! :)