# A research assistant made 160 mg of radioactive sodium (Na^24) and found that there was only 20 mg left 45 h later, what is the half-life of Na^24?

##### 1 Answer

Apr 12, 2017

The half life is

#### Explanation:

There are 2 ways for solving this problem

Every half life, the amount is divided by

After

After

After

The half life is

The half life of sodium 24 is

The radioactive decay constant is

We apply the equation

The activity is proportional to the mass.