Atoms and Nuclei


   
 
Numerical 12
12. The half-life of 92U238 against alpha decay is 4.5 x 109 years. How many disintegrations per second occur in 1 g of 92U238 ?

Suggested solution:

 
 
Again, since one k mole of any isotope contains Avogadro's number of atoms, there fore 1 g of 92U238 contains
 
Half life T = 4.5 109 years
 
Again, since one k mole of any isotope contains Avogadro's number of atoms, therefore 1g of 92U238 contains,
 
= 4.20 x 10-6k mole x 6.025 x 1026 atoms / k mole
 
= 25.3 x 1020 atoms
 
Decay rate,
 
 
                                   = 1.23 x 104 s-1
 
  
     
   
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