# Radon-222 has a half-life of 92.hours. How long would it take for the activity of a sample of the gas to be reduced to about 3% of its initial value?

##### 1 Answer

Oct 17, 2016

#### Answer:

It would take 19. days for the radon to decay.

#### Explanation:

The formula for the half-life of a first-order process is

#color(blue)(bar(ul(|color(white)(a/a) t_½ = (ln2)/kcolor(white)(a/a)|)))" "#

∴

The integrated formula for a first-order process is

#color(blue)(bar(ul(|color(white)(a/a) ln("A"_0/"A") = ktcolor(white)(a/a)|)))" "#