Chapter 7 Flashcards
Isolated system
cant exchange energy or matter with surroundings
closed system
can exchange energy, not matter
open system
can exchange energy and matter
First law of thermodynamics
Delta U= Q-W
U is internal energy
Q is heat added
W is work done
isothermal
constant temp, U is constant
Q=W
area is W
Adiabatic
No heat exchanged, thermal energy is constant
Q=0, delta U= -Q
change in U= work done on system= opposite work done by
isobaric
constant pressure
Area=W
isochoric
volumetric, no change in volume, no work
Delta U= Q
no area, no work
state function
describes system in equilibrium state
dont describe process, path independent
pressure, density, temp, volume, enthalpy, internal E, gibbs, Entropy
process function
describes pathway between equilibrium state
Work and Heat (Q)
standard conditions
25 C, 1 atm, 1 M
is most stable state
dont use for ideal gas
critical point
where liquid and gas line ends- no distinction between phases
have equal densities
Temperature
average KE
as enthalpy increases, temp. increases
absolute zero
when one cannot lose anymore thermal energy
heat
Q, transfer of energy due to differences in temp.
zero law of thermodynamics
when temps are equal, objects are at thermal equilibrium
first law of thermodynamics
delta U = Q-W
enthalpy
delta H
is Heat (Q) at constant pressure
calorimetry
used to measure heat transfer
bomb calorimeter has constant V
heat equation
q=mc (delta)t
specific heat
amount of energy to raise 1g by 1 C
C of water is 1 cal/gK
Heat capacity
MC
Why does phase change occur at a constant temp
substance absorbs heat energy and overcomes attractive forces to create a phase change
phase change equation
q=ml
L= latent heat
may need to add Q
enthalpy
H, heat changes at constant pressure
is path independent
standard enthalpy of formation
enthalpy to produce 1 mole of compound from its elements in their standard states
standard enthalpy of reaction
enthalpy change of reaction at standard conditions
Hess Law
enthalpy change of reactions are additive
Bond enthalpies
average energy to break a bond in gas phase
average of many different compounds
is endothermic
= H bonds broken- H bonds forms
second law of thermodynamics
energy spontaneously disperses from localized to spread out
entropy
measure of spontaneous dispersal of energy at a specific temp.- pathway independent
delta S= Qrev/T
increases when given energy
How does entropy in the universe work
change in S universe= S system + S surroundings >0
is always increasing
gibbs free energy
Measure of enthalpy and entropy during a process
max energy released available to do work
Delta g= delta H - T delta S
+ S and +H outcome
spontaneous at high T
- S and +H outcome
non spontaneous
+ S and - H outcome
spontaneous at all temp
-S and -H outcome
spontaneous at low temp
Delta G reaction standard
= -RTlnKeq
greater Keq is more negative delta G
delta G reaction not standard
Delta G standard + RTlnQ= RT ln(Q/Keq)
if Q > Keq, +ln, + delta G= reverse
