Question

1) Please show me the work and answer for this question.

Isotope X has a half life of 10 days. A sample is known to have 1000 radioactive atoms. How many atoms will remain radioactive after 30 days?

2) I also needed help on this postlab question: Can we use colorimetry to study all chemical reactions? Explain your answer. I know that it's no but why?

Answer 1

1) Given: t^1/2 = 10 days; initial amount No = 1000 atoms; total time T = 30 days; remaining amount N = ?

From equation, N = No(1/2)ⁿ

where n = number of t^1/2   and here, n = T/t^1/2 = 30/10 = 3

So, N = 1000(1/2)³

N= 1000/8

N = 125 atoms

2) Chemical colorimeters are devices that test for the presence of normally colorless chemicals in water by causing them to develop a color reaction and then comparing the results to a known body of data about the reactions of different substances. The limitation of the chemical colorimeter is that some substances have variances that can cause an inaccurate test result. As these variances are different for every substance, the chemical colorimeter alone is not a completely foolproof testing device, according to Global Water Instrumentation.