1. The following mechanism has been proposed for a reaction.
NO(g) + Br2 (g) = NOBr2(g)
NOBr2(g) + NO(g) = 2NOBr(g)
a) What compound is called the intermediate?
b) Write the rate law for each step of the mechanism.
c) If the first step is the slow step in the mechanism, what would the overall rate expression be?
2. Define the terms and differentiate between them:
rate constant, rate, rate equation
intermediate, activated complex, transition state
catalyst, inhibitor
energy of activation, energy of reaction.
3. Sketch the energy profile for a two step reaction. The first step has an activation energy of 70 kJ and forms and intermediate 50 kJ above the reactants' energy. The second step has an energy of activation of 40 kJ. Overall the enthalpy of reaction is endothermic by 20 kJ. Indicate the position of the two activated complex or transition states and also indicate the position of the reactants, the products, and the intermediate.
4. List three different ways that are commonly used to speed up a reaction.
5. Use the reaction: 2 HI = H2 + I2 to illustrate a reaction energy profile and what is meant by activated complex or transition state and what is meant by energy of activation and energy of reaction.n
6. Show how NO might catalyze the conversion of SO2 +O2 to give SO3.(Hint. NO is known to rapidly react with O2 to form NO2 which in turn can react with SO2).
Note: Catalysts are frequently put above a reaction arrow to indicate they used to speed up the reaction even though they are not used in the reaction stoichiometry. Write that nomenclature for the balanced overall reaction for the above process.
7. What is an enzyme?
8. What is the difference between and order of a reaction
and the molecularity of the reaction?
What is the difference between a mechanism and an overall reaction?
What is the difference between the energy of activation of a reaction
and the change in energy (or enthalpy) of a reaction?
9. Give three common (and equivalent) ways of expressing
the units of a second order rate constant.