What is the percentage of the initial activity of phosphorus

2· P decays by -emission and has a half-life of 14.2 days. Write a balanced nuclear equation for the decay of a. . 32 1 p b. After 550days what percentage of the initial activity of P remains?

Solution

1) first order kinetics

K1 = 0.693/t1/2

   = 0.693/14.2

   = 0.049 day-1

k1 = (1/t)ln(a0/a)

a0 = initial concentration = 100%

a = concentration remains after 55 days = x

t = 55 days

0.049 = (1/55)ln(100/x)

x = 6.75%