Name:  _____________________                              date:  __________________               period: _______

Kinetics & nuclear chemistry               test                              60 points (3 ec)                                                chemistry

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

1. It takes 3.5 years for a hypothetical radioactive isotope to go from 25 mg to 5.0 mg; what is its decay constant ? [5 points]

2. A hypothetical sample had 25 mg 3H originally, but now has only 5.0 mg 3H.  The half-life of 3H is about 12.3 years.  What is the age of the sample ?  [10 points]

3. What does the terms in the equation, E = m c 2 mean ?  [5 points]


4. Fill-in the below blanks of the (hypothetical ?) nuclear reactions.  [10 points]

a.  alpha decay of 225Ra:  _________________________________

b. beta decay of 45Ca:  _____________________________________

c.   50Ti  -->   ______  +  7Be   and the type of nuclear reaction is  _________________

d. 55Cr  +  28Al  -->   _____   +  37S     and the type of nuclear reaction is  ____________

5. Fill-in the below table in regards to the chemical reaction:  N2  +  3 H2  -->  2 NH3.  [18 points]

Rate (mM / sec)

Δ [N2] / Δt (mM /sec)

Δ [H2] / Δt (mM /sec)

Δ [NH3] / Δt (mM /sec)

6.0

 

 

 

 

 

-36

 

 

 

 

24

6. Based on the below information, determine the rate law for the reaction: N2  +  3 H2  -->  2 NH3.   [15 points]

expt

Δ [NH3] / Δt (mM /sec)

[N2] (mM)

[H2] (mM)

1

0.001

2.0

2.0

2

0.002

8.0

2.0

3

0.002

2.0

4.0