Tbr lecture 3 passage 14

[yellowjellybean]

---

Members don't see this ad.

Hey guys, I just posted a question a few days ago but ran into another one I'm having trouble with.


Consider the following endothermic equation:

1 N2O4(g) <--> 2NO2(g)

As the handle of a piston container filled with an equilibrium mixture of NO2 and N2O4 is lifted, what occurs?

I.The PNO2/PN2O4 ratio increases.
II. The piston cools down
III. The mole percent of N2O4 increases.

I'm having trouble with statement II. I used pv=nRT but in the answers it says " do not mistakenly think of pv=nrt because the temperature was not changed to cause the volume or pressure change." I have no idea what this means and why I can't use pv=nrt.

Thank you

 

[chenzt]

In this situation, P went down, but V went up. PV = Constant that didn't change before the handle was lifted and after. Temp change only if P*V changes, which requires an input or output of energy (since temperature is the expression of avg energy in the system).