Hi all.
I'm trying to become acquainted with thermal dynamics. I thought I had a fairly good handle on the idea gas law, PV=nRT, or PV=mRT, but I came across a problem involving the throttling of an idea gas, and the solution was totally not what I expected. Referring to picture where gas is forced through the valve I thought I tried using:
[itex]\frac{P_{1}V_{1}}{T_{1}}[/itex] = [itex]\frac{P_{2}V_{2}}{T_{2}}[/itex]
Setting V[itex]_{1}[/itex] = V[itex]_{2}[/itex], then solving for T[itex]_{2}[/itex]:
T[itex]_{2}[/itex] = [itex]\frac{P_{2}T_{1}}{P_{1}}[/itex]
Of course I got the wrong answer. The solution explained that the throttling process produces no change in enthalpy for an idea gas, and therefore no temperature change. I'm trying to follow they're explanation, but what I'm more interested in understanding is why the application of the idea gas law is not valid for this situation. I would expect it to be valid in any situation with an idea gas, so obviously I'm misusing it. Could someone explain to me why it's not valid in this situation? Thanks a lot.
I'm trying to become acquainted with thermal dynamics. I thought I had a fairly good handle on the idea gas law, PV=nRT, or PV=mRT, but I came across a problem involving the throttling of an idea gas, and the solution was totally not what I expected. Referring to picture where gas is forced through the valve I thought I tried using:
[itex]\frac{P_{1}V_{1}}{T_{1}}[/itex] = [itex]\frac{P_{2}V_{2}}{T_{2}}[/itex]
Setting V[itex]_{1}[/itex] = V[itex]_{2}[/itex], then solving for T[itex]_{2}[/itex]:
T[itex]_{2}[/itex] = [itex]\frac{P_{2}T_{1}}{P_{1}}[/itex]
Of course I got the wrong answer. The solution explained that the throttling process produces no change in enthalpy for an idea gas, and therefore no temperature change. I'm trying to follow they're explanation, but what I'm more interested in understanding is why the application of the idea gas law is not valid for this situation. I would expect it to be valid in any situation with an idea gas, so obviously I'm misusing it. Could someone explain to me why it's not valid in this situation? Thanks a lot.