1 / 39

Chapter 14

Chapter 14. Kinetics. Kinetics. Defined:. Factors that affect Rate. Review…. In any equation Reactants  products N 2(g) + 3H 2(g)  2NH 3(g) Equilibrium. RATE. Speed of the Reaction Measure either. Rate Equation. Rate =. Rate Equation. Rate =. Rate Equation. Average Rate =.

bobby
Download Presentation

Chapter 14

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Chapter 14 Kinetics

  2. Kinetics • Defined:

  3. Factors that affect Rate

  4. Review… • In any equation • Reactants  products • N2(g) + 3H2(g)  2NH3(g) • Equilibrium

  5. RATE • Speed of the Reaction • Measure either

  6. Rate Equation Rate =

  7. Rate Equation Rate =

  8. Rate Equation Average Rate =

  9. Instantaneous Rate

  10. Rate and Concentration • Generally, rate decreases as time passes. • Why?

  11. Study rate by looking at NH4(aq)+ + NO2-(aq)  N2(g) + 2H2O(l) See table 14.3 pg 516

  12. Rate Law • Rate = • Must determine the value of k, the rate constant • Choose one set of data… • Look at the units

  13. Practice • Using previous rate law, what is the rate when the concentration of each reactant is 0.334 M? K= 2.7 x 10-4 M-1s-1

  14. Reaction Order • If rate law = k[react 1]m[react 2]n • The exponents are

  15. Units of rate constants • Depend on the • Rate units are • Rate constant units must allow that

  16. For example • Second order reaction • Units of rate =

  17. Determining Rate Law • Must be determined experimentally • Compare rates as concentration of reactants is changed

  18. Condition 1 • Change concentration =

  19. Condition 2 • Change in concentration = • Double concentration = • Triple concentration =

  20. Condition 3 • Double concentration = • Triple concentration =

  21. Rate aA + bB  cC + d D

  22. Dependence of Rate on Concentration

  23. Conditions for Rxn • Orientation of molecules • Energy, specifically, Kinetic Energy

  24. Reactive Collisions • Both previous conditions met • KE is easy to change

  25. Activation Energy, Ea • Minimum energy needed for reactive collision • Increase T means • Ea is also energy required to make

  26. Activated complex • When reacting molecules ‘stick’ together before completing reaction • They must have • Intermediate species

  27. Reaction completes • When activated complex breaks apart • New molecules result from this process • No activated complex left in system

  28. Exothermic Reactions • Stored chemical energy • Disorder • Products at

  29. Endothermic Reactions • Energy is • Increase of • Disorder • Products at

  30. Direction of Reaction • Forward • Reverse • One is favorable • Tendency to increase • Tendency to decrease

  31. Heat of reaction • Hrxn • Enthalpy of reaction • Measure of the energy change • Formula • Hrxn = Ef – Er

  32. Exo or Endothermic? • If H > 0 kJ • Reaction is • + sign tells you • If H < 0 kJ • Reaction is • - sign tells you

  33. Practice • What is the Hrxn if the Energy of the forward reaction is 65 kJ and that of the reverse is 32? • Is this reaction exo or endothermic?

  34. Catalysts • Something that increases the rate of reaction • Not consumed • Provides a • ‘Helps’ in the formation of the activated complex

  35. Formation of Acid Rain • Coal and sulfur • Produce SO2 in cars and energy plants • Reacts with water in air • Needs NO as

  36. Catalysts • Decrease Ea • Do not change the • Only change the • Provides a

  37. Enzymes • CO2 + H2O  H2CO3 • Carbonic anhydrase • Enzyme (-ase is the key) • Facilitates conversion • Changes the rate by a factor of 3.5 x 106

  38. Enzyme/Substrate Complex • Decreases • Therefore increases • High Ea = • Low Ea =

More Related