1. Nov 2, 2008

Andrusko

1. The problem statement, all variables and given/known data
A source contains two radioactive isotopes of phosphorus. P-32 has a half life of 14.3 days and P-33 has a half-life of 25.3 days.

If 10% of the radioactive decays from the source are from P-33 atoms, calculate the ratio of the number of P-33 to P-32 in the source. The answer says 5.1 : 1.

2. Relevant equations

$$T_{1/2} = \frac{ln2}{\lambda}$$

3. The attempt at a solution

Well I have calculated decay constant, but I don't know what to do with any of it. I really have no idea where to start.

decay constant P-32 = 5.61E-7 s^-1
decay constant P-33 = 3.17E-7 s^-1

I tried:
$$0.1 = \frac{P_{33}}{P_{33} + P_{32}}$$

and rearranged and got 9. Which isn't 5.1. Last time I checked, anyway.

Last edited: Nov 2, 2008