# Radioactive iodine-131 has a half-life of eight days. The amount of a 200.0 gram sample left after 32 days would be?

##### 1 Answer

Jul 3, 2014

#### Explanation:

Nuclear half-life,

In this question, the half-life of iodine-131 is

- after
#8# days (the first half-life):

#"200 g" /2 = "100 g"# decays and#"100 g"# are left.

- after another
## days (two half-lives or # 16# years):

#"100 g" /2 = "50 g"# decays and#"50 g"# are left.

- after another
#8# days (three half-lives or#24# years):

#"50 g" /2 = "25 g"# decays and#"25 g"# are left.

- after another
#8# days (four half-lives or#32# years):

#"25 g"/2 = "12.5 g"# decays and#"12.5 g"# are left.

So after four half-lives or