Question

How much Na-24 is consumed in 24 hrs if the half life of Na-24 is 15.02 hrs and initial amount is 5.0 mg?

---please explain how you solved this. I'm stuck on this problem and I have a test coming up on this stuff, so I very desperately want to understand!

Answer 1

According to half life equation (1/2) ^{number of half lives} equals to the decimal amount remaining

half life of sodium Na-24 = 15.02

number of half lives after 24 hr=24/15.02=1.597

1.597 number of half life reuired after 24 h

the decimal amount remaining after 24 h=(1/2)^1.597= 0.330

so we have to calculte how much remained after 24 h and the intial amount 5.0 mg

the amount left after 24 h= intial amount x 0.330=5x0.330=1.65 mg

the amount consumed after 24 h= intial amount- left amount after 24 h=5.0 -1.65=3.35 mg