Alright so I can't figure this one out:
In a free adiabatic expansion, a real gas is allowed to spread to twice its original volume with no energy transfer from the surroundings. All of the following are true concerning this process EXCEPT:
A) No work is done.
B) Increased potential energy between molecules results in decreased kinetic energy and the gas cools.
C) Entropy increases
D) The gas loses heat.
The answer is D. I thought it was a throw-up between B and D. I know the system can't lose energy to its surroundings (specifically through work via heat to the system's surroundings) but why is B true? I don't understand how potential energy increases. Also, if the gas cools ...doesn't that mean the gas loses heat? The gas's heat gets turned into potential energy... ? I can't conceptualize this at all.
Also, I know it's a lot to cover, but why is dH = q when pressure is held constant? I've kinda just accepted it up til this point, ha.
And why isn't dH = q when volume is held constant? The way I rationalized it goes something like this:
deltaH = deltaE + PdeltaV
dH = (q - w) + PdV
dH = (q - 0) + 0 when volume is constant.
So I understand why E = q when volume is held constant, but why not dH?
Can someone explain via equations? I'd appreciate any help provided. Thanks in advance! 🙂
In a free adiabatic expansion, a real gas is allowed to spread to twice its original volume with no energy transfer from the surroundings. All of the following are true concerning this process EXCEPT:
A) No work is done.
B) Increased potential energy between molecules results in decreased kinetic energy and the gas cools.
C) Entropy increases
D) The gas loses heat.
The answer is D. I thought it was a throw-up between B and D. I know the system can't lose energy to its surroundings (specifically through work via heat to the system's surroundings) but why is B true? I don't understand how potential energy increases. Also, if the gas cools ...doesn't that mean the gas loses heat? The gas's heat gets turned into potential energy... ? I can't conceptualize this at all.
Also, I know it's a lot to cover, but why is dH = q when pressure is held constant? I've kinda just accepted it up til this point, ha.
And why isn't dH = q when volume is held constant? The way I rationalized it goes something like this:
deltaH = deltaE + PdeltaV
dH = (q - w) + PdV
dH = (q - 0) + 0 when volume is constant.
So I understand why E = q when volume is held constant, but why not dH?
Can someone explain via equations? I'd appreciate any help provided. Thanks in advance! 🙂