Kinetics Review Questions1. Define rate of reaction

2. What are the units of the rate of reaction?

3. Draw a graph that shows the concentration of products with time as a reaction goes to completion. Explain the shape of the graph.

4. On the same graph, using a different color or dotted line, show how the concentration of products changes with time when a catalyst is added.

5. Draw a graph that shows the concentration of reactants with time as a reaction goes to completion. Explain the shape of the graph.

6. On the same graph, using a different color or dotted line, show how the concentration of reactants changes with time if a lower concentration (through an increased volume so that the total number of moles is the same) is used.

7. True or false: All collisions result in a reaction.

8. What are the 4 parts of collision theory and why is it important?

9. Give two reasons why a collision would not result in a reaction

10. The reaction between nitrogen and oxygen in the atmosphere under normal conditions is extremely slow. Which statement best explains this?

A. The concentration of oxygen is much lower than that of nitrogenB. The molar mass of nitrogen is less than that of oxygenC. The frequency of collisions between nitrogen and oxygen molecules is lower than that between

nitrogen molecules themselvesD. Very few nitrogen and oxygen molecules have sufficient energy to react

11. List 4 factors that affect reaction rates

12. Define activation energy

13. Sketch a Maxwell-Boltzmann Energy Distribution Curve for two different temperatures.

14. Does activation energy change with temperature?

15. How does the number of molecules with the required activation energy change at higher temperatures? Use energy distribution to explain.

16. Give two reasons why a temperature increase, increases reaction rate and identify the more important reason.

17. Explain, using the Maxwell-Boltzmann Energy distribution, why adding a catalyst increases reaction rate.

18. Will the following changes increase the reaction rate of the following reaction when 50 cm3 of 1.0 mol dm-3 HCl is added to 1.0 g calcium carbonate?

CaCO3(s) + 2 HCl (aq) CaCl2 + CO2(g) + H2O(l)

a. increasing volume of HClb. increasing mass of CaCO3c. decreasing size of CaCO3 particlesd. decreasing amount of CO2 present

e. increasing temperaturef. adding water to the reactiong. removing water from the reaction vesselh. adding a catalyst

Kinetics Review Anwers

19. Define rate of reaction

Rate of reaction: change in concentration of reactant or product with time

20. What are the units of the rate of reaction? Units: Molarity/time or mol dm-3 s-1

21. Draw a graph that shows the concentration of products with time as a reaction goes to completion. Explain the shape of the graph.

22. On the same graph, using a different color or dotted line, show how the concentration of products changes with time when a catalyst is added.

23. Draw a graph that shows the concentration of reactants with time as a reaction goes to completion. Explain the shape of the graph.

24. On the same graph, using a different color or dotted line, show how the concentration of reactants changes with time if a lower concentration (through an increased volume so that the total number of moles is the same) is used.

25. True or false: All collisions result in a reaction.

26. What are the 4 parts of collision theory and why is it important?

- reactions occur when molecules collide- they must collide with the right orientation- they must collide with enough activation energynot all collisions result in a reaction.

27.Give two reasons why a collision would not result in a reaction not enough energy, not the right orientation

28. The reaction between nitrogen and oxygen in the atmosphere under normal conditions is extremely slow. Which statement best explains this?

E. The concentration of oxygen is much lower than that of nitrogenF. The molar mass of nitrogen is less than that of oxygenG. The frequency of collisions between nitrogen and oxygen molecules is lower than that between

nitrogen molecules themselvesH. Very few nitrogen and oxygen molecules have sufficient energy to react

29. List 4 factors that affect reaction rates

Surface area: the larger the surface area, the higher the possibility for collision, the fast the rate

Concentration: the larger the concentration, the higher the possibility for collision, the faster the rate

Catalyst: lowers the activation energy so more molecules have the required Ea and therefore there are more successful reactions

Temperature: at higher temperature the molecules are moving faster and colliding more. More molecules have the required activation energy so even more collisions will be successful.

30.Define activation energy Minimum energy needed for a reaction to occur.

31. Sketch a Maxwell-Boltzmann Energy Distribution Curve for two different temperatures.

EaEnergy

Number of Molecules

32.

33.Does activation energy change with temperature? NO!!!

34. How does the number of molecules with the required activation energy change at higher temperatures? Use energy distribution to explain.

At higher temps, the peak of the curve shifts to the right, showing that more molecules (given by area under the curve) have the required Ea.

35. Give two reasons why a temperature increase, increases reaction rate and identify the more important reason.

at higher temperature the molecules are moving faster and colliding more frequently. More molecules have the required activation energy so even more collisions in a given amount of time will be successful. The latter is most important.

36. Will the following changes increase the reaction rate of the following reaction when 50 cm3 of 1.0 mol dm-3 HCl is added to 1.0 g calcium carbonate?

CaCO3(s) + 2 HCl (aq) CaCl2 + CO2(g) + H2O(l)

increasing volume of HCl No, because the concentration is not changingincreasing mass of CaCO3 Depends, if you were just adding more CaCO3 of the same size particles than the rate would probably increase. If you added more mass by adding one large chunk that had less surface area than before, the reaction could slow down. decreasing size of CaCO3 particles increases

decreasing amount of CO2 present increases if you assume the reaction was at equilibrium to start with. In the beginning, removing CO2 would have no affect on the rate of reaction.increasing temperature increasesadding water to the reaction decreases because concentration is decreased.removing water from the reaction vessel increases because concentration is increased.adding a catalyst increases.

37. Explain, using the Maxwell-Boltzmann Energy distribution, why adding a catalyst increases reaction rate.

Catalyst lowers activation energy. So the Ea on the boltzmann graph shifts left. The area under the curve, and above Ea is larger than when Ea is higher (no catalyst). More molecules have the required activation energy so there will be more successful collisions in a given amount of time.

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