Ch. 19 nuclear chem  test           [45 points]                            Chemistry

 

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. 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 (spontaneous) fission of 235Ra involving 140Ba:  ______________________________

 

2. A hypothetical radioactive isotope took 10.0 days to go from 40.0 mCi to 10.0 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.   [15 points]

 

   a. What is the isotope’s half life ?  [hint:  see italicize text]

 

   b.  What is the isotope’s decay constant ?

 

   c. What is the age of the sample ?


3.
 Describe the basis of the atomic bomb; include / define the terms, critical mass and chain reaction in your response. [15 points; hint:  involves an induced nuclear fission reaction]