Question

Which radioactive isotope would have the longer half- life ¹⁵O or ¹⁹O? (Given rate constants for ¹⁵O and ¹⁹O are 5.63 x 10^-3 s^-1 and k = 2.38 x 10^-2s^-1 respectively.) 

a. ¹⁵O

b. ¹⁹O

c. Both will have the same half-life

d. None of the above, information given is insufficient

Answer 1

Correct option is a. ¹⁵O

The rate constant for the decay of O-15 is less than that for O-19. Therefore, the rate of decay of O-15 will be slower and will have a longer half life.