Exam 3 – Thermodynamics Review
FIRST LAW OF THERMODYNAMICS
Energy cannot be created or destroyed
E
q w
∆ =
+
E
∆
is a state function meaning that only the final and initial positions are important.
Heat and work are NOT state functions.
What does this mean?
+q
heat is absorbed by the system
q
heat is released by the system
+w
work is done on the system by surroundings
w
work is done by the system on the surroundings
Paths
•
Against a constant pressure
ext
W
P
V
= 
∆
If an ideal gas expands against a constant external pressure of 1.20 atm from a
volume of 20.0 L to a volume of 50.0 L.
During the expansion, the gas absorbs
2500 J of heat.
Determine
E
∆
.
(Remember conversion factor!)
•
Expansion Work
reversible, isothermal
2
1
ln
V
W
nRT
V
= 
What is the maximum work done when 1.00 moles of gas expands from 1.00 L to
10.0 L at a constant temperature of 25
o
C?
Other Descriptions of Energy Change
V
E
nC
T
∆ =
∆
This preview has intentionally blurred sections. Sign up to view the full version.
View Full DocumentENTHALPY
We know that under isobaric conditions
p
E
q
W
∆ =
+
We define change in enthalpy as the amount of heat released or absorbed during a
This is the end of the preview.
Sign up
to
access the rest of the document.
 Spring '08
 Kenney
 Thermodynamics, Entropy, entropy change, total entropy, Thermodynamics Energy

Click to edit the document details