Question

one isotope of chromium has a half life of 18 hours. How long does it take 100 grams to decay to 20 grams?

Answer 1

41.79 hours

Explanation:

The Half-time Decay Formula:
`N=N_0((1)/(2))^(t)/(d)`

Where
`N_0` is the original number, and t = time, and d = time it takes to half

18 would be d

100 would be
`N_0`

and 20 would be N

`20=100((1)/(2))^(t)/(18)`

`0.2=((1)/(2))^(t)/(18)`

`log_(1)/(2)0.2=(t)/(18)`

`18* log_(1)/(2)0.2=t`

`18* (log_(10)0.2)/(log_(10)(1)/(2))=t`

= 41.79470571