Factors Affecting RXN Rates

2. Factors Affecting RXN Rates • Nature of Reactants • Temperature • Concentration • Surface Area • Catalysts/ Inhibitors

3. Catalyst • Catalysts speed up reactions. (enzymes) Inhibitors • Inhibitors slow down reactions (preservatives)

4. Catalyst / Inhibitors • A substance NOT permanently changed during the reaction. • Changes energy needed to start reaction

5. Catalytic converter • Enzymes

6. Activation Energy • Energy needed to start reaction

9. Energy Diagram

10. Heat of Reaction: DH • Difference between the STORED Energy of the products and energy of the reactants DH = PEp - PEr Change in heat products reactants

11. Endothermic reaction • Energy is absorbed (in). • Surroundings get colder • Eproducts > Ereactants • ▲H is positive

12. Products have more Energy

13. Exothermic Reaction • Energy is released (out) • surrounding get hotter • Ereactants > Eproducts • ▲H is negative

14. Products have less Energy

16. Catalyzed Reactions d9 c23

17. Hydrogen peroxide Rxt. C34

18. Catalyst • Works by changing the activation energy required • The lower the Ea the greater the rate of the reaction.

20. Inhibitors d9 c38 • Works by changing the activation energy required • The greater the Ea the lower the rate of the reaction.

21. Energy Diagram Ea Inhibitors