Question

The percent natural abundance of 40K is 0.0117%. The radioactive decay of 40K atoms occurs 89% by β− emission; the rest is by electron capture and β+ emission. The half-life of 40K is 1.26×109 years.

Calculate the number of β− particles produced per second by the 40K present in a 1.49 g sample of the mineral microcline, KAlSi3O8.

Answer 1

- 1.49g of sample of KAISE 308 Solution % of K in KAIS*30g - Mass of K Kloo Mass of kalsi 308 0 x 100 278.33 - 14.05% mass of k in 1.49g sample is 1.498 14.05 loo of k that we have = 0.2093 gram. then - Mass Number of nok nucle" = (moles of K x Avo garso Nox. abundance E. 2093 x(6-02 x 1023) (0.000117) 40 3.685xlo Then Activity = NX. where d = en (2)

A= 3.685x 107 x ln (2) P26x109 x (365) x (24)x 60 x 60 A = 2.55uaxlo17 1,26 x(365) x624) x 6X6 x 10" 6.42 decars f sec A = B then emission number occur 89% ß- particle produced is = 89% of activity = 89 x 6.42 100 = 5.7138 B particle produced per second