Question

The radioactive nuclides Pt - 199 has a half-life of 30.8 minutes. A sample is prepared that has an initial activity of 7.56 x 10^11Bq. a) How many Pt -199 nuclei are initially present in the sample?
b) How many are present after 30.8 minutes?
c) What is the activity at this time?

Answer 1

a)

$$N_0=\frac{A}{\lambda}=\frac{7.56 \cdot 10^{11}(30.8\cdot60)}{\ln{2}}=2.02\cdot 10^{15}$$

b)

$$N=0.5^{\frac{\tau}{\tau}}N=0.5(2.02\cdot 10^{15})=1.01\cdot 10^{15}$$

c)

$$A(t)=0.5^{\frac{\tau}{\tau}}A=0.5(7.56 \cdot 10^{11})=3.78 \cdot 10^{11}\ Bq$$