Iron-59 is a beta emitter with a half-life of 44.5 days. if a sample initially contains 180 mg of iron-59, how much iron-59 is left in the sample after 267 days?

2.79 mg iron-59 is left in the sample after 267 days.

Explanation:

Given that:

Half life = 44.5 days

Where, k is rate constant

So,  

The rate constant, k = 0.0156 days⁻¹

Using integrated rate law for first order kinetics as:

Where,  

is the concentration at time t

is the initial concentration  = 180 mg

Time = 267 days

So,  

2.79 mg iron-59 is left in the sample after 267 days.

idk i’m struggling too

the answer is 75.0%.