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Rates Of Reaction

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Published in: Chemistry
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How far the rate of reaction goes and how much reaction is being consumed and how much product is being produced over a period of time? This all you can find over here .

Wardah M / Dubai

9 years of teaching experience

Qualification: BSc Physics, BDS , Masters in Biochemistry

Teaches: Science Projects, Biology, Chemistry, Biochemistry, SAT, EMSAT, IGCSE/AS/AL, IB Exam Preparation, Physics, Science, Exam Preparation, General Science, English, Maths, Mathematics

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  1. Kinetics How fast the reaction goes? What does that mean?
  2. Kinetics How much reactant is being consumed? How much product is being produced over a period of time? Can we speed it up or slow it down? What is the relationship between the reactants? What is happening on the molecular level?
  3. Rate Appreciation 1) Slow - aging process 2) Medium - burning of a candle mass before - mass after - time - 3) Fast - flash paper
  4. Rate Description Rate or Speed = change in observational property time Observational property: Change in 1) mass 3) color 2) concentration (M/time) 4) temp 5) pH
  5. Rate Description Calculate the rate of wax burning: Huge on units!
  6. Problem Important! Once you have one rate you can stoich the other rates. EX 2 N205 4 N02 +02 Initial rate of reactant consumed is .025 M/S What is rate of appearance for N02 and 02?
  7. Problem 2 N205 4 NO 2 + 02 Initial rate of reactant consumed is .025 M/S N02: .025 N205 4 N02 = 2 N205 .025 N205 2 N205 .050 M/S .013 M/S
  8. Average Rate Given to you in a table: Ex Rate of N205 Decomposing 4.2 x 10-5 2.8 x 10-5 2.0 x 10-5 1.4 x 10-5 1.0 x 10-5 Time 0-50 sec 50-100 sec 100-150 sec 150-200 sec 200-250 sec What do you observe?
  9. Average Rate Why would the rate slow down?
  10. Average Rate Problem Consider the hypothetical reaction: 2A+ B 2C+D Some point during the reaction .2885 M and 2.55 min later, [D] — .3546 M. What is the average rate of reaction during this time in M/min? What is the rate of formation of C expressed in M/sec?
  11. Instantaneous Rate Using a graph: Can be found by taking the slope of the line tangent to the curve at that point. x
  12. Instantaneous Rate Problem Using the graph you've been given, determine the instantaneous rate of disappearance At 300 seconds At 0 seconds
  13. Initial Rate of Reaction Take the instantaneous rate at the beginning
  14. Collision Theory Reactions happen when reactants COLLIDE
  15. Collision Theory Why does the rate go down as the reaction proceeds? 1) Need Collisions - collisions cause reactions!!!! Less stuff -> Less collisions
  16. Collision Theory Why does the rate go down as the reaction proceeds? Need a Certain Amount of Energy -> Activation Energy(Ea) is the minimum amount of energy required to produce a reaction. Very few have the same activation energy
  17. Collision Theory A Maxwell-Boltzmann distribution can be used to predict fraction of successful collisions activation energy energy
  18. Collision Theory Why does the rate go down as the reaction proceeds? 3) Need the correct Orientation-> the right kind of geometry! Therefore not all collisions produce reactions.
  19. Factors Affecting Rate Nature of reactants -> Demo Something in the bonds of the reactants that influences rate. Weak bonds react quicker=need less activation energy
  20. Factors Affecting Rate Concentration -> Demo Greater amount of reactants - greater # of collisions - greater # of right kind of collisions.
  21. Factors Affecting Rate Surface Area - Demo Increase S.A. will increase the amount that will react - greater # of collisions - greater # of right kind of collisions.
  22. Factors Affecting Rate Temperature - Demo Increasing temp increases average KE- greater # of collisions - greater # of right kind of collisions. Note: If the reaction is fast already, inc temp won't have much effect.
  23. Factors Affecting Rate Adding a Catalyst - Demo It decreases the activation energy
  24. Activity IODINE CLOCK reactions competition