Transcript Wednesday, September 5

Spontaneity
Spontaneity
A reaction is spontaneous if it sill
occur with no outside intervention.
Spontaneity
4Fe + 3O2 → 2Fe2O3
∆H = -1625 kJ
Spontaneity
CH4 + 2O2 → CO2 + 2H2O
∆H = -891 kJ
Spontaneity
CH4 + 2O2 → CO2 + 2H2O
∆H = -891 kJ
Some spontaneous reactions need
a little bit of activation energy.
Spontaneity
Are all spontaneous reactions
exothermic?
Spontaneity
entropy
Spontaneity
chaos
Spontaneity
disorder
Spontaneity
randonmess
Entropy
Entropy
always
Entropy
always
wins.
Spontaneity
A reaction is spontaneous
if entropy increases.
Spontaneity
A reaction is spontaneous
if entropy increases.
ΔSsystem =
ΔSproducts - ΔSreactants
Spontaneity
Entropy usually increases when:
•Liquids vaporize
•Solids melt
•Dissolved gasses bubble out
•The number of gaseous particles
increases
•Solids or liquids dissolve
•Temperature increases.
Spontaneity
Predict the sign of ΔS:
ClF(g) + F2(g) → ClF3(g)
Spontaneity
Predict the sign of ΔS:
NH3(g) → NH3(aq)
Spontaneity
Predict the sign of ΔS:
CH3OH(l) → CH3OH(aq)
Spontaneity
Predict the sign of ΔS:
C10H8(l) → C10H8(s)
Spontaneity
The biologist’s question:
Spontaneity
The biologist’s question:
If entropy always
increases, how do life
forms grow, develop, and
evolve?
Spontaneity
ΔSuniverse =
ΔSsystem + ΔSsurroundings