unit 3

Question 1

1. The rate of a reaction may be affected by
   a) the nature of the reactants
   b) the concentration of the reactants in the rate-determining step
   c) the reaction temperature
   d) the presence of a catalyst
   e) all of the above

Answer 1

E

Question 2

2. Chemical kinetics is best defined as the study of
   a) exothermic and endothermic reactions
   b) first-order and second-order reactions
   c) reaction rates and mechanisms
   d) activated complexes and activation energy
   e) heterogencous and homogencous catalysts

Question 3

3. The concentration of a reactant that is changed to product in a definite period of time is its
   a) rate of mass action
   b) catalytic rate
   c) rate constant
   di rate of reaction
   e) activation energy rate

Question 4

4. For any chemical reaction, the rate law
   a) can be predicted from the overall chemical equation
   b) can be determined from reaction orders
   c) can be predicted from overall reaction order
   d) depends upon the state of the reactants must be determined experimentally

Question 5

5. The rate-determining step in a neaction mechanism must be the
   8) middle step b) fastest step
   c) slowest step d) first step e) last step

Question 6

6. Sawdust is blown into some types of furnaces to increase the rate at which wood burns because the
   a) surface area of reacting particles is increased
   b) reacting particles become ionic
   c) reacting particles become molecules

Question 7

7. In general, the rate of a reaction can be doubled by
   a) doubling the mass of the reactants.
   b) reducing the volume of the reaction flask
   c) doubling the observation time
   d) doubling the reaction temperature
   © raising the temperature 10 °C

Question 8

7. In general, the rate of a reaction can be doubled by
   a) doubling the mass of the reactants.
   b) reducing the volume of the reaction flask
   c) doubling the observation time
   d) doubling the reaction temperature
   © raising the temperature 10 °C

Question 9

8. Raising the temperature of a reaction mixture increases the rate of the reaction but does NOT significantly increase the
   a) activation energy b) average velocity of the reacting molecules. ) number of collisions
   d) number of successful collisions
   e) fraction of the reacting molecules that possess energies greater than activation energy

Question 10

9. A match, at room temperature, does not ignite spontaneously with oxygen in the air because
   a) the reaction is endothermic
   b) the reaction is exothermic
   c) very few molecules have acquired sufficient activation energy
   d) air is only about 20% oxygen

Question 11

step 1: BrO: + 2H* => HaBrO,*
step 2: Br* + H.BrO,=> Br-BrOz + HO
step 3: Br-BrO, + 4 H + 4 Br* = 3 Bra + 2 H0
10. Which one of the following equations could be the overall equation for the proposed reaction mechanism above?
a) Br + BrO, + 6H* = Bo + 3 HO
b) 2 Br03- + 12 H* => Bro + 6H20
c) 2 Br* +6H20 => 2 BrOs + 12 H*
d) 5 Br + BrO, + 6H* => 3Bn + 3 H0
e) 2H6B-03* + 2H* => Bo + 3H0

Question 12

11. If the rate-determining step in the proposed reaction mechanism is step 2, increases the concentration of which species will increase the overall rate of reaction?
    a) Br-BrOz and H20
    b) HoBrO: and H*
    c) BrO; and Br
    d) Br-BrOz and BrO3*
    (e) Brand HoBrOr*

Question 13

15. Which one of the following statements about the reaction pathway in the presence of a catalyst is FALSE?
    a) The catalyst increases the rate of rxn of both the forward and the reverse processes
    b) The catalyst enables the reaction to proceed more rapidly at a lower temperature
    c) The catalyst involves the formation of an activated complex
    d) The catalyst lowers the AH of the reaction
    c) The catalyst is not used up overall.