Topic Potential Energy Curve Do Now p 26

Topic: Potential Energy Curve Do Now: p. 26

Spontaneous Processes =physical or chemical change that occurs with no outside intervention Iron rusting 4 Fe(s) + 3 O 2(g) 2 Fe 2 O 3(s) H = -1625 k. J • However, some energy may be supplied to get process started = activation energy Combustion CH 4(g) + 2 O 2(g) CO 2(g) + 2 H 2 O(l) H = -891 k. J

Can you think of others?

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Activation Energy & Reaction

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 Reaction Activated Complex = intermediate formed during conversion from reactants to products Reactants 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. 2. 3. 4. 5. 6. PE reactants PE products PE activated complex Ea forward reaction Ea reverse reaction H

Enthalpy 40 30 Ea forward rxn 20 10 Ea reverse rxn PE reactants PE activated complex PE products Time What kind of reaction is represented?

Enthalpy 40 30 20 10 H of reaction

Enthalpy 40 30 20 PE of reactants Ea forward rxn Ea reverse rxn PE of activated complex 10 P. E. of products Time What kind of reaction is represented?

Enthalpy 40 30 20 10 H of reaction

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