Question

Please help ASAP The half-life of cobalt-60 is 5 years. How old is a sample of cobalt-60 if only one-eighth of the original sample is still cobalt-60?

A. 5 years
B. 10 years
C. 15 years
D.20 years

Answer 1

15 years so C. edge 2023

Step-by-step explanation:

Answer 2

Answer:The correct answer is option C.

Step-by-step explanation:

Initial mass of the sample =
`N_o`

Sample left after t years ,=
`N=(N_o)/(8)`

Half-life of sample of cobalt-60
`t_{(1)/(2)}` = 5 years

`\lambda=\frac{0.693}{t_{(1)/(2)}}=(0.693)/(5 years)=0.1386 year^(-1)`

`N=N_o* e^(-\lambda t)`

`ln[N]=ln[N_o]-\lambda t`

`\log[([N_o])/(8)]=\log[N_o]-(\lambda t)/(2.303)`

`\log[(1)/(8)]=-(0.1386 year^(-1)* t)/(2.303)`

`t=15.33 years\approx 15 years`

Hence ,the correct answer is option C.