What's the use of density here?

[turtleGuy]

Pressure initial: 95 kPa
Final pressure: 190 kPa
Change in enthalpy: -2.96 kJ
Initial volume: 0.045 cu.meter
Density: 1.11 kg/cu.meter
pV=c

 

[Chestermiller]

Pressure initial: 95 kPa
Final pressure: 190 kPa
Change in enthalpy: -2.96 kJ
Initial volume: 0.045 cu.meter
Density: 1.11 kg/cu.meter
pV=c

Is there some sort of problem statement here?

 

[turtleGuy]

Is there some sort of problem statement here?

Oh. Sorry...
The problem is "What is the change in internal energy of ethane

 

[Chestermiller]

What are your thoughts on this?

 

[turtleGuy]

What are your thoughts on this?

I don't think it has any use.

W=pVln(P1/P2)
W=(95)(0.045)ln(95/190)
W=-2.96 kJ
Then,
Using : ΔU=Q-W
=-2.96kJ - (-2.96kJ)
=0 kJ

But I'm not sure about it

 

[Chestermiller]

Are you sure they said pV=c? Because, if that's so, then $\Delta (pV)=0$, which means that $\Delta U=\Delta H-\Delta (pV)=\Delta H$. That would suggest non-ideal gas behavior. Are you currently learning about non-ideal gas behavior?

Do they give any indication of which state the density refers to, initial or final? Are there additional parts to this problem statement?

 

[turtleGuy]

yeah they only said pV=constant. The density is on the Initial.

 

[Chestermiller]

yeah they only said pV=constant. The density is on the Initial.

pV being constant means that $\Delta U=\Delta H$. But, if these both are not equal to zero, that means that the behavior is inconsistent with the behavior of an ideal gas. So either, the gas is behaving non-ideally or there is inconsistency in the problem statement. So I ask again, are you currently learning about the behavior of non-ideal gases, or are you only covering ideal gases now?