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CHAPTER 18

CHAPTER 18. REACTION RATES & FACTORS AFFECTING EQUILIBRIUM. Activated Complex. A.E. E of reactants. 2H 2 + O 2. E. E of products. 2H 2 O. Energy Diagrams. Energy. Reaction Progress. A.E. (activation energy): minimum energy needed for a reaction to occur.

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CHAPTER 18

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  1. CHAPTER 18 REACTION RATES & FACTORS AFFECTING EQUILIBRIUM

  2. Activated Complex A.E. E of reactants 2H2 + O2 E E of products 2H2O Energy Diagrams Energy Reaction Progress A.E. (activation energy):minimum energy needed for a reaction to occur

  3. Not Every Collision Produces Products Reactants must: 1. Collide and 2. Have enough energy to produce products.

  4. http://www.mhhe.com/physsci/chemistry/essentialchemistry/flash/activa2.swfhttp://www.mhhe.com/physsci/chemistry/essentialchemistry/flash/activa2.swf

  5. Energy barrier w/o catalyst Energy barrier w catalyst Catalyst A substance that increases the rate of reaction without being used up itself in the reaction. Reactants Energy Products Reaction Progress

  6. Exothermic vs. Endothermic Exothermic: • A process that loses heat to its surroundings. Fe2O3(s) + CO(g) Fe(s) + CO2(g) + 26.3 kJ Endothermic: • A process that absorbs heat from its surroundings. 2NaHCO3(s) + 129 kJ Na2CO3(s) + H2O(g) + CO2(g)

  7. Is the following an example of an exothermic or endothermic reaction? Reactants Potential Energy EXOTHERMIC=energy is released Products Reaction Progress

  8. Is the following an example of an exothermic or endothermic reaction? Products Potential Energy Reactants ENDOTHERMIC=energy is absorbed Reaction Progress

  9. Factors Affecting Reaction Rates 1. Temperature 2. Concentration 3. Particle Size 4. Catalysts

  10. Factors Affecting Reaction Rates 1. Temperature WHY Temp Rate Kinetic Energy

  11. Factors Affecting Reaction Rates 2. Concentration WHY Conc. Rate More Particles increases collision frequency

  12. Factors Affecting Reaction Rates 3. Particle Size WHY Particle Rate Smaller Particle Size size increases the surface area

  13. Factors Affecting Reaction Rates 4. Catalyst WHY Adding a Rate Activation Energy Catalyst

  14. FACTORS AFFECTING EQ.Le Chatelier’s Principle Reactions will stabilize and establish equilibrium. If this system is disturbed from equilibrium, it will shift in order to reduce the disturbance. When any of the following three things are changed, the system will change to re-establish equilibrium. • Concentration • Temperature • Pressure System @ Equilibrium R P Systems not @ Equilibrium

  15. Concentration • If the concentration of the reactants or products is changed, the reaction will try to re-establish equilibrium H2CO3CO2 + H2O If we add CO2, more H2CO3 will be made If we remove CO2, more CO2 & H2Owill be made

  16. Concentration If we remove H2CO3, more H2CO3will be made H2CO3CO2 + H2O If we add H2CO3, more CO2 & H2O will be made

  17. Temperature • If the temperature is changed, the reaction will try to re-establish equilibrium. 2SO2 + O2 2SO3 + heat If we add heat, more reactants will be made in order to absorb the excess heat If we remove heat, more products will be made in order to replace the heat that has been removed.

  18. Pressure • If the pressure is changed, the reaction will try to re-establish equilibrium. N2 + 3H2 2NH3 If we increase pressure, more products will be made (less molecules) 4 molecules If we decrease pressure, more reactants will be made (more molecules) 2 molecules

  19. R = P Review Reactions will stabilize and establish equilibrium. When any of the following three things are changed, the reaction will change to re-establish equilibrium. • Concentration • Temperature • Pressure

  20. CHAPTER 18 Spontaneous vs. Nonspontaneous Reactions

  21. Spontaneous reactions: 1. Favor the formation of products. 2. Give off free energy. -Free energy: energy available to do work Ex: Only 30% of energy is used to propel a car by burning gasoline. 70% is wasted as heat.

  22. Spontaneous reactions: 3.Entropy (S): the disorder of a system -Spontaneous rxns occur when a system moves in the direction of disorder. 4. Enthalpy (H): heat -Spontaneous rxns occur when the system is exothermic.

  23. NonSpontaneous reactions: 1. Do not favor the formation of products.

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