Untitled - Kelly Walsh High School

Kinetics 201
energy of a reaction. Catalysts are substances that speed up the rate of reaction
without being consumed in the reaction. They affect the reaction rate by lowering
the activation energy by providing a reaction surface and orientation or
by providing an alternate mechanism (pathway). We may gather information
concerning the reaction mechanism from the rate laws.
1. What five factors can affect the rate of a chemical reaction?
2. The rate of a reaction increases by a factor of nine when the concentration
of one of the reactants is tripled. The order with respect to this reactant is
_____.
3. The rate of a reaction does not change when the concentration of one of the
reactants is tripled. The order with respect to this reactant is _____.
4. What is the equation for the half-life of a second-order reaction?
5. A student calculates the activation energy for a reaction and gets 0.12 J/mol.
What is wrong with this answer?
6. True/False. An automobile catalytic converter is an example of a heterogeneous
catalyst.
7. True/False. You can get a rate law directly from a balanced chemical
equation.
8. True/False. You can get a rate law directly from the rate-determining (slow)
step in a mechanism.
9. True/False. Termolecular (three molecules) steps are common in mechanisms.
10. True/False. The mechanism for a reaction with the rate law, Rate
k[A] 2 [B], will have a step where two molecules of A collide with a molecule
of B.
11. A certain substance undergoes a first-order reaction with a rate constant of
1.25 hr 1 . How long will it take for the concentration of this reactant to
drop from 1.0 M to 0.38 M?
12. Determine the half-life of a second-order reaction if the rate constant is
1.78 M 1 s 1 . The initial concentration is 0.575 M.
13. Nitrosyl chloride, NOCl, decomposes as follows:
2 NOCl(g) l 2 NO(g) Cl 2(g)
This reaction has a rate constant of 9.3 10 5 M 1 s 1 at 100°C, and 1.0
10 3 M s 1 at 130°C. Determine the value of the activation energy in kJ/mol.
ANSWER KEY
1. Nature of the reactants, the temperature, the concentration of the reactants,
physical state of the reactants, and catalysts
2. 2 3. 0 4. t1/2 1/k [A] 0