24.2: Mass Defect & Half Lives
Chapter 24

Dr. Robert E. Belford




Question 1
Given the following masses:

4He = 4.0026 g/mol

9Be = 9.0778 g/mol

12C = 12.0000g/mol

1n = 1.00866g/mol.

Calculate the energy released for the following reaction:

He + Be --> C + n


(A)  -3.56 x 109 J
(B)  -6.46 x 1012 J
(C)  -8.77 x 1023 J
(D)  6.24 x 1013 J
 
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Question 2
How many grams of 222Rn are left after 7.0 days if a sample originally had 100.0 g and the half life is 3.82 days?
(A)  67.3 g
(B)  0.10g
(C)  28.1 g
(D)  9.89 g
 
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Question 3
How many grams of 226Ra are left after 7.0 days if a sample originally had 100.0 g and the half life is 8.0x104years?
(A)  0.124 g
(B)  100.0 g
(C)  45.0 g
(D)  1.070x10-12 g
 
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Question 4
How many grams of 214Po are left after 7.0 days if a sample originally had 100.0 g and the half life is 1.6-4seconds?
(A)  0.00
(B)  38.4 g
(C)  100.0 g
(D)  0.125 g
 
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