3. You propose two reaction mechanisms for a reaction you are studying. You experimentally determine that the overall reaction is 1st order with respect to (CH3)3CBr and Oth order with respect to cyanide. Which mechanism(s) is/are valid? Explain your answer. Mechanism A Step 1: (CH3)3CBr (CH3)3C + Br -> Step 2: (CH3)3C + CN→ (CH3)3CCN Overall: (CH3)3CBr + CN→ (CH3)3CCN + Br Mechanism B Single-step: (CH) CBr + CN (CH) CCN + Br 4. On the axes below, draw the energy diagram of a one-step, exothermic reaction with an activation energy of 40 kJ/mol and a AH of -30 kJ/mol. Then, draw another curve corresponding to the reaction in the presence of a catalyst that reduces the activation energy by 20 kJ/mol. 100 80 80 00 10 Energy (kJ/mol) 20 20 reactants Reaction progress

For each of the following reaction diagrams, estimate the activation energy (Ea) of the reaction:

The acid-catalyzed iodination of acetone CH3COCH3(aq) + I2(aq) CH3COCH2I(aq) + HI(aq) is a common laboratory experiment used in general chemistry courses to teach the method of initial rates. The reaction is followed spectrophotometrically by the disappearance of the color of iodine in the solution. The following data (J. P. Birk and D. L Walters, Journal of Chemical Education, Vol. 69, p. 585, 1992) were collected at 23 C for this reaction. Determine the rate law for this reaction.

The decomposition of azomethane, (CH3)2N2, to nitrogen and ethane gases is a first-order reaction, (CH3)2N2(g)N2(g)+C2H6(g). At a certain temperature, a 29-mg sample of azomethane is reduced to 12 mg in 1.4 s. (a) What is the rate constant k for the decomposition at that temperature? (b) What is the half-life of the decomposition? (c) How long will it take to decompose 78% of the azomethane?

The reaction of compound A to give compounds C and D was found to be second-order in A . The rate constant for the reaction was determined to be 2.42 L/mol/s. If the initial concentration is 0.500 mol/L, what is the value of t1/2?

There are two molecules with the formula C3H6 Propane, CH3CH = CH2, is the monomer of the polymer polypropylene, which is used for indoor-outdoor carpets. Cyclopropane is used as an anesthetic: When heated to 499 C, cyclopropane rearranges (isomerizes) and forms propane with a rate constant of 5.95104s1. What is the half-life of this reaction? What fraction of the cyclopropane remains after 0.75 h at 499 C?

The rate constant for the ?rst-order decomposition at 45 C of dinitrogen pentoxide, N2O5, dissolved in chloroform, CHCI3, is 6.2104 min-1. 2N2O54NO2+O2 What is the rate of the reaction when [N2O5] = 0.40 M?

Consider a reaction of the type aA products, in which the rate law is found to he rate = k[A]3 (termolecular reactions are improbable but possible). If the first half-tife of the reaction is found to he 40. s, what is the time for the second half-life? Hint: Using your calculus knowledge, derive the integrated rate law from the differential rate law for a tennolecular reaction: Rate=d[A]dt=k[A]3

For each of the following reaction diagrams, estimate the activation energy (Ea) of the reaction:

The label on a bottle of 3% (by volume) hydrogen peroxide, H2O2, purchased at a grocery store, states that the solution should be stored in a cool, dark place. H2O2decomposes slowly over time, and the rate of decomposition increases with an increase in temperature and in the presence of light. However, the rate of decomposition increases dramatically if a small amount of powdered MnO- is added to the solution. The decomposition products are H2O and O2. MnO2 is not consumed in the reaction. Write the equation for the decomposition of H2O2. What role does MnO2 play? In the chemistry lab, a student substituted a chunk of MnO2 for the powdered compound. The reaction rate was not appreciably increased. WTiat is one possible explanation for this observation? Is MnO2 part of the stoichiometry of the decomposition of H2O2?