Gen Chem Day 7 Flashcards
change in heat, not state funciton
Q
a function that only depends upon the inital and final states of the system, being independent of the pathway taken
state function
Enthalpy
H
exothermic
H<0 releases heat
endothermic
H>0 needs heat
change H=
qp… pressure of heat
Hess’s law… ways to calculate H
pick the ones that add up to your goal
Bond dissociation energy
Change H= sum D broken- sum D formed
Bond breaking is
endothermic
Bond making is
exothermic
Enthalpies of Formation
change H= sum n H products - sum n H reactants
forms 1 mole of a single substance from its component elements in their standard states
formation rxn
Calorie
1000 cal
Calorimetry
q=CchangeT or q=mcchangeT
Entropy (S)
phases of matter S=sum S products - sum S reactants… focus on moles
c= specific heat
4.184 J/ g*c
Temp does
Not change during phase change
G<0
spontaneous
G>0
nonspontaneous
G=0
at equilbrium
Gas in a piston
- Transfer of heat (lock piston)
2. Expanding gases cool; compressing gases warm (real, not ideal)
Isobaric
(change P=0… no change in pressure
isochoric
change V = 0 so w=0… no work
isothermal
change T =0 so change E=0 NOCHANGE
Adiabatic
q=0 anti temp exchange… no temp change
Zeroth law
concept of thermal equilibrium and temp
- thermodynamics
energy can be neather created nor destroyed
2 thermodynamics
for a spontaneous process, the entropy of the universe increases… system vs surrouding
3 thermodynamics
a perfect crystal at 0K has zero entropy
change E=
q+w
w=
-Pchange V
change G=
sum n G products- sum n G reactants
change G=
change G degree + RTlnQ
change G=
-RTlnKeq
change S=
change H/ T
change G=
change H- T change S
H- S-
sponateous at low temp
H+ S+
spontaneous at high tem
H- S+
always sponteous
H+ S-
non spontaneous at all temps
Expansion
v>0, w<0
compression
v0
