1. List at least four observations that would indicate a chemical reaction is taking place.

2. Color Change Energy change (heat/light) )

3. Production of a solid Production of a gas

4. Do reactions only procede forward (R → P) or can they go also go in reverse (P → R)? Reversible reaction Link to phet reversible REACTIONS CAN GO IN BOTH THE FORWARD AND REVERSE DIRECTIONS! Link to Chemical Oscillator

5. Link to Rings of Color NO! ALL CHEMICAL REACTIONS IN A CLOSED SYSTEM WILL EVENTUALLY REACH CHEMICAL EQUILIBRIUM Link to Briggs-Rausher

6. NO Color CHANGES NO Temperature CHANGE NO solid or gases products appearing

7. Reaction Simulation Activity: Partner Activity, 1 cup of beans between two partners R P Overall Rxn Rate = Difference between forward rate (R → P) and reverse rate (back rate, P → R). Equation for rate: Rate = k[N], where k = rate constant and N is # of reacting particles. We will simulate a reaction with a forward rate constant k = ½ and a back rate, k = ¼. Forward Rate: Rate = ½[N] Reverse Rate: Rate = ¼[N]

8. Table #1: Round #1 Reactant Person: Rate = ½[40] = Product Person: Rate = ¼[0] = Reactant person transfer 20 to product person; product person transfer zero back; Each partner count total and record results in outcome. 20 0

9. TABLE 1 R R P P # OF BEANS # TRANSFERRED # OF BEANS # TRANSFERRED INITIAL 40 ----------------- 0 1 ST TRANSFER ------------- - --------------- OUTCOME --------------------- ----------------- 20 0

10. Table #1: Round #2 Reactant Person: Rate = ½[20] = Product Person: Rate = ¼[20] = Reactant person transfer 10 to product person; product person transfer 5 back; Each partner count total and record results in outcome. Work through rounds 3 & 4 on your own. Round fractions. Example #1: 15 ÷ 2 = 7.5 → 8 Example #2: 25 ÷ 4 = 6.25 → 6 10 5

11. TABLE 1 R R P P # OF BEANS # TRANSFERRED # OF BEANS # TRANSFERRED INITIAL 40 ----------------- 0 1 ST TRANSFER ------------- - --------------- OUTCOME --------------------- ----------------- 2 ND TRANSFER ------------- - --------------- OUTCOME --------------------- ----------------- 3 RD TRANSFER ------------- - --------------- OUTCOME --------------------- ----------------- 4TH TRANSFER ------------- - --------------- OUTCOME --------------------- ----------------- 20 0 10 5 15 13 8 6 25 27 13 27 7 7

12. TABLE 2 R R P P # OF BEANS # TRANSFERRED # OF BEANS # TRANSFERRED INITIAL 40 ----------------- 20 ----------------- 1 ST TRANSFER ------------- - --------------- OUTCOME --------------------- ----------------- 2 ND TRANSFER ------------- - --------------- OUTCOME --------------------- ----------------- 3 RD TRANSFER ------------- - --------------- OUTCOME --------------------- ----------------- 4TH TRANSFER ------------- - --------------- OUTCOME --------------------- ----------------- 20 5 25 35 13 9 21 20 11 10 39 40 20 40 10

13. Questions (After 4 th transfer) 1) Compare # beans transferred R → P to R ← P. 2) Compare forward and back rates: 3) Is outcome changing? 4) Ratio of P/R in table 1 and table 2 5) Term for forward rate = back rate and [R] and[P] are constant: # is EQUAL; Table #1 7:7 ; Table #2: 10:10 NO; Table #1 13:27 ; Table #2: 20:40 RATIO P/R FOR BOTH ≈ 2. Table #1 27/13 ; Table #2: 40/20 EQUILIBRIUM

14. Table #1 Graph: #Beans vs. outcomes # BEANS INITIAL 1 ST OUT 2 ND OUT 3RD OUT4TH OUT 10 20 30 40 0 EQUILIBRIUM

15. Table #1 Graph: #Transferred vs. transfer step # TRANS 1 ST Trans 2 ND Trans 3 RD Trans4 th Transfer 5 10 15 20 0 EQUILIBRIUM

16. Chemical Equilibrium

17. NET Concentrations of Reactants and Products are constant (not changing) Forward Rate = Reverse Rate No visible changes taking place

18. Dynamic Equilibrium – at equilibrium the forward and backward reactions are still taking place but at equal rates Link to phet reversible

19. NO 2 ↔ N 2 O 4 Link to NO2 equilibrium McGraw Hill

20. At what point (A,B, or C) has chemical equilibrium been reached? C B A

21. C B A

22. At point A, which is faster the forward or reverse reactions? At which point has chemical equilibrium been reached? A B C

23. A B C

24. HW 11-3, p. 543, #3-12 (WB, p. 100) 3) How do chemists envision reactions taking place in terms of a collision model For reactions? Give an example of a simple reaction and how you might envision the reaction taking place by means of collisions between molecules.

25. Summary OF Collision Theory RXN RATE = RXN RATE = # of collisions x fraction with correct energy x fraction with correct orientation

26. HW 11-3, p. 543, #3-12 (WB, p. 100) 4) What does the symbol Ea stand for and what does it represent in terms of a chemical reaction? Ans: Ea = Activation Energy; the minimum amount of energy needed to initiate a chemical reaction.

27. HW 11-3, p. 543, #3-12 (WB, p. 100) 5) A catalyst works by providing an alternative pathway by which the reaction may take place with reaction having a lower than the pathway followed when the catalyst is not present. 6) What are enzymes and why are they important? Ans: Enzymes are proteins which catalyze chemical reactions in cells. Without enzymes, the chemical reactions needed to sustain life would be too slow. Activation Energy

28. HW 11-3, p. 543, #3-12 (WB, p. 100) 7) How does equilibrium represent a balancing of opposing processes? Give an example of an “equilibrium” encountered in everyday life, showing how the opposing processes oppose each other. Possible Answer: If population of a town is 100,000 at the beginning and end of a year, best explanation is an equal # of people moved in and out of town, not that no one moved in or out during an entire year.

29. HW 11-3, p. 543, #3-12 (WB, p. 100) 8) How do chemists define a state of chemical equilibrium? 9) What does the use of a double arrow, indicate about a chemical reaction? Ans: Reaction is reversible. Reactants and products are interconverted back and forth. NET Concentrations of Reactants and Products are constant (not changing) Forward Rate = Reverse Rate No visible changes taking place

30. HW 11-3, p. 543, #3-12 (WB, p. 100) 11) What does it mean to say that a chemical or physical equilibrium is dynamic? Answer: The forward and reverse reactions are still taking place, but at equal rates.

31. 12) For the reaction H 2 O + CO ↔ H 2 + CO 2. What is the significance of the portion of the plot where the two main curves join together to form a single curve as time increases? H 2 O + CO → H 2 + CO 2 H 2 + CO 2 → H 2 O + CO