Nuclear chemistry & kinetics test [85 points] Chemistry

For problems involving calculations, show your work in an organized manner, includes any relevant formula / equation, the proper units in your work / answer, and the proper number of significant figures in your answer.

1. Fill-in the blank or write the (hypothetical) nuclear reaction. [15 points]

a. alpha decay of 230Ra: __________________________

b. beta-minus decay of 40K: ________________________

c. 35S --> 35P + _______

d. 18O --> 18F + ______

e. 235Th  -->  55Cr + _____

2. In the reaction: N 2 + 3 H 2  -->  2 NH 3 if , then [10 points]

a. = ____

 

b. = _____

3. The half-life of 131I is 8.06 days. [15 points]

a. determine the decay constant

b. How long would it take for a 250 mCi sample of 131I to decay to 100 mCi ?

4. An unknown radioactive isotope takes 15 years to decay from 735 Bq to 300. Bq. [15 points]

a. determine the decay constant

b. A sample of this isotope that originally contained 385 mCi, currently has 38 mCi. What is the “age” of the sample ?

5. For the reaction: N2 + 3 H -->  2 NH3 , the following (hypothetical) experimental data was obtained:

expt

Rate (mM/s)

[N2] (M)

[H2] (M)

1

9

2

3

2

9

4

3

3

36

2

6

Determine the rate law (include the value of the exponents, the rate constant and the units of the rate constant) [15 points]
6. sketch and label (the axis of the graph & Ea,f , Ea,b, and ∆H) a reaction energy profile, where [15 points]

a. Ea,f = 255 kJ /mole and ∆H = - 25 kJ /mole.

b. Ea,f = 325 kJ / mole and Ea,b = 275 kJ / mole

c. the effect of a catalyst on a reaction’s energy profile