Ch. 14 & 21 nuclear chem. & kinetics            test       85 points                                AP chem

 

 

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:  ___________________

 

 

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. 

 

1.  A sample containing 2.5 * 1015 radioactive isotope has a radioactivity of 25 μCi; Ci = 3.7 * 1010 disintegration / second.  [10 points]

 

a.  what is the decay constant of this isotope ?

 

b.  what is the half-life of the isotope ?

 

2.  fill-in the blank for the following hypothetical nuclear reactions.  [10 points]

 

a.  81Rb undergoing electron capture:  ______________________

 

b.  alpha decay of 122Sn:  ______________________________

 

c.  190à   90Sr  +  ____  & type of reaction =  ____________

3.  A sample containing a hypothetical radioactive isotope with a half-life of 225 years currently has 375 mg, while there was originally 1.2 g.  What is the “age” of the sample ?  [10 points]

 

 

4.  It took 25.0 years for a hypothetical radioactive isotope to decay from 275 Bq to 125 Bq.  What is the half-life of the isotope ?  [10 points]


 

5.  Describe the graphical analysis to determine the activation energy of a reaction; include the basis / rationale of your analysis.   [10 points]

 

 

6.  Describe the graphical analysis to determine if a reaction:    A  +  B  à  AB

is 0th, 1st, or 2nd order with respect to A and briefly describe the necessary experimental condition(s).  [hint:  your kinetics lab;  15 points]


 

7.  Determine the rate law for the synthesis of ammonia from hydrogen and nitrogen based on the following hypothetical experimental data; include the value & units of the rate constant.  [20 points]

 

expt

[N2]  (M)

[H2] (M)

Initial   (mM / s)

1

2.0

1.0

1.0

2

2.0

4.0

2.0

3

3.0

9.0

4.5