Liter atm mole joules mole consider internal energy
August 27, 2001
| q | ∆U |
|---|
Sign conventions:
q > 0: heat input into the system from the surroundings.
w > 0: work done by the system on the surroundings. ∆U >0: when the internal energy of the system increase.
V=V(P,T); P=P(V,T); T=T(P,V)
U=U(P,T) = U(P,T) = U(P,V)
Treating U as a state variable: V=V(U,P) or V=V(U,T), etc.
Idea gas:
|
VP T 0 0 | ) | = | V P T 0 , ) |
|
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|---|---|---|---|---|---|---|---|---|---|
| T 0 | T | ||||||||
| = | cons | . | |||||||
| PV | = | P V 00 | |||||||
| T | |||||||||
| U | = | N | ⋅ | (3 | k T | ) | = | 3 | RT |
|
|---|---|---|---|---|---|---|---|---|---|---|
| 2 | B | 2 |
Usually, gases at very low pressures can be modeled as an idea gas because the interactions between particles are very weak.
| C |
|
|
||||||
|---|---|---|---|---|---|---|---|---|
| C V | δ q | �� | V | |||||
| dT | � | |||||||
| C | P | = � | δ q | � |
P |
|
||
| � | dT | |||||||
| w | = | 2 | PdV | = | 2 | = | P V | 2 | − | V 1 | ) | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| � | P dV� | |||||||||||
| 1 | 1 |
From the First Law
| ( U | 2 | + | PV | 2 | ) | − | ( U | 1 | + | PV 1 | ) | = | qp |
|---|
Then for an isobaric process,
| H | 2 | − | H | 1 | = ∆H | = | qp |
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