Question

The half-life of a certain isotope is 15 minutes. How much of a 400 g sample will remain after 90 minutes? 12.5 g6.25 g26.7 g66.7 g 25 g

Answer 1

There is a total of 6 half lives that need to take place.

ONE HALF LIFE = 200

TWO HALF LIFES = 100

THREE HALF LIFES = 50

FOUR HALF LIFES = 25

FIVE HALF LIFES = 12.5

SIX HALF LIFES = 6.25

The answer is 6.25g