# chemistry

posted by .

What is the half-life of an isotope if it decays to 12.5% of its radioactivity in 18 minutes?

• chemistry -

ln(100/12.5) = k*18
Solve for k, then
k = 0.693/t(sub>1/2.
Solve for t1/2.

• chemistry corr'n -

k = 0.693/t1/2

## Similar Questions

1. ### chemistry

If there are 80 milligrams of a radioactive element decays to 10 milligrams in 30 minutes then what is the elements half life in minutes?
2. ### Chemistry

Gallium65, a radioactive isotope of gallium, decays by first order-kinetics. The half-life of this isotope is 15.2 min. How long would it take for 7/8 of a sample of this isotope to decay?
3. ### Chemistry

As a sample of the radioactive isotope 131 I decays, its half-life a)decreases b)increases c)remains the same
4. ### Chemistry

I've figured out most of it. I'm not sure how to find the percentage ofd the isotope. Define the half life. The half-life of a radioisotope is found to be 4.55 minutes. If the decay follows first order kinetics, what percentage of …
5. ### College Algebra

Use a calculator to help solve the problem. One isotope of holmium, 162Ho, has a half life of 22 minutes. The half-life of a second isotope, 164Ho, is 37 minutes. Starting with a sample containing equal amounts, find the ratio of the …

How are the terms "activity" and "becquerel" related?