topic: potential energy curve do now: p.26. spontaneous processes no outside intervention =physical...
TRANSCRIPT
Topic: Potential Energy Curve
Do Now: p.26
Spontaneous Processes=physical or chemical change that occurs with no outside intervention
• However, some energy may be supplied to get process started = activation energy
Iron rusting4Fe(s) + 3O2(g) 2Fe2O3(s)
H = -1625 kJ
Combustion CH4(g) + 2O2(g) CO2(g) + 2H2O(l) H = -891kJ
Can you think of others?
VIDEO
Activation Energy
• = Energy needed to initiate reaction
• Energy needed to overcome reaction barrier
• difference between where reactants start & top of hill
• Difference between reactants & activated complex
Energy Diagram of a ReactionActivated Complex = intermediate formed during conversion from reactants to productsReactants combine to form an unstable complex
Potential Energy Curve: Endothermic
Products have more P.E. than reactants
Start low, end high
Potential Energy Curve: Exothermic
Products have less P.E. than reactants
Start high, end low
Have to label 6 energies on curve: reactants & products
1. PE reactants2. PE products3. PE activated complex4. Ea forward reaction
5. Ea reverse reaction
6. H
Time
What kind of reaction is represented?
PE reactants
PE activated complex
PE products
Ea forward rxn
Ea reverse rxn
40
30
20
10
Enth
alpy
H of reaction
40
30
20
10
Enth
alpy
Time
What kind of reaction is represented?
PE of reactants
PE of activated complex
P.E. of products
Ea forwardrxn
Ea
reverserxn
40
30
20
10
Enth
alpy
H of reaction
40
30
20
10
Enth
alpy
Catalyst (in the body = enzyme)
• Substance that increases rate of reaction without itself being consumed –does not participate in reaction
• Lowers the activation energy for the reaction
DOES IT AFFECT ΔH?Catalysts do not affect ΔH