1. Which peak on the energy diagram (lab manual) for this experiment represents
ID: 881451 • Letter: 1
Question
1. Which peak on the energy diagram (lab manual) for this experiment represents the transition state in which water has reacted with the carbocation? a. the second peak b. the third peak c. the first peak d. this is not present on the diagram
2. When comparing SN1 versus SN2 reactions, which one is a one-step reaction and in which is the rate of reaction not affected by nucleophilic strength? a. SN1,SN2 b. SN1,SN1 C. SN2,SN1 D.SN2,SN2
3.Why do the coefficients of an elementary step equal the reaction orders of its rate law, but those of an overall reaction do not?
A. This is generally not true, the coefficients cannot be used for the reaction orders of its rate law for either type of reaction.
B.An elementary step uses an average reaction rate calculation while the overall reaction uses an instantaneous rate calculation.
C. Overall reactions are always in dynamic equilibrium while elementary steps are not.
D.An elementary step is a single molecular event and occurs in one step, but the overall reaction is generally a series of elementary steps which are not necessarily proportional to the product of the overall reaction concentrations.
4. If a small amount of acetone you are using in this experiment spills on the countertop, what should you do?
A.Neutralize the liquid with base.
B.Test its acidity with bromophenol blue indicator.
C.Neutralize the liquid with acid.
D.Clean it up with paper towels.
5.Cyclobutane (C4H8) decomposes in a first-order reaction, with a rate constant of 87 s-1, to form two molecules of ethylene (C2H4). If the initial concentration is 3 M, what is the concentration after 0.040 seconds? Please round your answer to one significant figure.
6.Cyclopropane thermally decomposes by a first order reaction to form propene. If the rate constant is 6.8 s–1, what is the half–life of the reaction?
7.How long does it take for the concentration to reach 0.50 of its initial value?
Explanation / Answer
answer 1) a) second peak
answer 2) c) SN2, SN1
answer 3) D) An elementary step is a single molecular event and occurs in one step, but the overall reaction is generally a series of elementary steps which are not necessarily proportional to the product of the overall reaction concentrations.
answer 4) Clean it up with paper towels.
answer 5) For the First order rate is given by
k = 2.303/t log a/a-x
Given k = 87 /sec a = 3 M ,a-x= ? t = 0.04 sec
87 = 2.303/0.04 * log 3/a-x
log 3 / 3-x = 1.511
3/3-x = 32.4339
and 3-x = 0.0924 M
answer 6) using the formula
half life time(t1/2) = 0.693/k
given k=6.8/sec
= 0.693/6.8 = 0.101 sec
answer 7) given k = 0.68
k = 2.303/t log 2a/ a
= 2.303/t log 2
t = (2.303/0.68) *(log 2)
t = 3.3867 *0.3010 = 1.01 sec
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