Ch. 21 & 14  nuclear chem. & kinetics             test     [100 points]                 AP Chem

 

For problems involving calculations, show your work in an organized manner, include any relevant equation (or formula and conversion factor(s)), put the proper units in your calculations / answer, and have the proper number of significant figures in your answer. 

 

Academic Honesty:   The answers on this test are my own and I am using only the allowed set of notes as described in the syllabus.  I have not discussed the test questions with anyone before or during the test nor have I seen the test questions prior to the exam.  If you violate any of the preceding items or do not sign, your semester grade is a F.

 

                                                                                                Signature:  ___________________

 

  1.  A hypothetical radioactive isotope took 5.0 days to go from 25.0 mCi to 20.0 mCi; Ci = Curie = 3.7 * 1010 isotopes disintegrate per second.  A sample originally contained 125 nanomoles of this isotope; currently there is 75.0 nanomoles of the isotope.  What is the age of the sample ?   [10 points]

 

 

2. Fill-in the blank; write the nuclear equation describing the following (hypothetical ?) nuclear reaction.  [15 points]

 

   a.  the alpha decay of 235Th:   _____________________________________

 

   b.  the positron emission of 45Ca:  __________________________________

 

   c. the fission of 235Ra involving 140Ba:  ______________________________

 

2.  10.0 nanomoles of a hypothetical radioactive isotope has a radioactivity of 25.0 μCi.  What is the half-life of this isotope (in years) ?  [15 points]

 

 

3. In the combustion of ethane, the rate of the appearance of water is 10.0 mM / second.  Based on this information, what is __ ?  [15 points]

 

     a. the relationship between   d[O2] / dt, the rate of the reaction, and the rate of the appearance of water ? the rate of the reaction ?

      b.  In regards to a catalyst,  [15 points]

c. what is it’s effect on the rate of a reaction ? 

 

4. sketch a reaction energy profile of an exothermic reaction – for the uncatalyzed  versus catalyzed reaction; label the energy level of the product,  energy level of the reactant, and the activation energy of the forward & backward reactions. 

 

 

5.  Referring to the reaction energy profile, the Arrenhius equation, and the rate law, rationalize the effect of a catalyst on the rate of a reaction.

 

 

6.  In regards to your crystal violet kinetics lab

 

purple dye  +  OH-  à  colorless dye

 

describe the experimental procedure and subsequent data analysis to determine the rate law.  While specific volumes and concentrations are not needed to describe the experimental protocol, do not mention the relative concentrations of the chemicals in the reaction.  [30 points]