Name:  ______________                                                                    date:  ____________

 

Nuclear Chemistry & kinetics                test  [100 points]                      Chemistry

 

 

Show your work, include any equation / formula used to get your answer, the proper units in your work / answer, the proper number of significant figures in your answer, and circle your answer.  Pick any 5 problems; the first 5 problems will be scored, unless you clearly state the problems to be scored.

 

  1. Fill-in the blank for the following nuclear (hypothetical ?) nuclear reactions.

 

 

a.  2512Mg (undergoes beta minus decay)  à _____   +   _____

 

 

b.  2211Na (undergoes beta plus decay)  à  _____   +   _____

 

 

c.       _____  à  alpha particle  +  13956Ba

 

 

d.      _____  à  9038Sr  +  7633As

 

 

e.       4020Ca  +   _____  à  5626Fe

 

  1. A radioactive sample originally contained 800 mCi, which decayed to 100 mCi in 30.0 days. 
    1. What is the half-life of this isotope ?

 

 

    1. What is the decay constant ?

 

  1. A sample originally contained 80 mg of a radioactive isotope, where the sample currently contains 8.0 mg of the isotope.  The half-life of the isotope is 500 years. 

 

    1. What is the decay constant of the isotope ?

 

 

    1. what is the “age” of the sample ?

 

  1. Fill-in the below table in regards to the reaction:  CH3OH  +  O2  à  CO2  +  H2O.  units:  mM / sec.  Show / label your work below the table.

 

Rate

CH3OH / t

O2 / t

CO2 / t

H2O / t

a.

  XXXXX

- 30

b.

c.

d.

e.

f.

   XXXXX

60

12

g.

h.

i.

j.

 

5.  Sketch/ draw / label the reaction energy profile, where

    1. Ea,b = 20 kJ / mol  and  H = - 30 kJ / mol,  then determine Ea,

 

 

    1. Ea,f = 50 kJ / mol  and  Ea,b  =  20 kJ /mol,  then determine H

 

6.  Determine the rate law (include all exponents and the rate constant with the proper units) of the following reaction:     C  +  H2  +  O2  à  CH3OH

based on the following experimental data:

 

Rate (mM / sec)

[C]  (mM)

[H2]  (mM)

[O2]  (mM)

1.25 * 10-6

10

10

10

5.0 * 10-6

20

10

10

1.25 * 10-6

10

40

10

2.5 * 10-6

10

10

20