Question

A first order decomposition reaction has a half-life of 64yr. What percentage of the original amount is left after 135years. (give answer to 1 decimal place)?

Answer 1

Answer:

23.2%

Step-by-step explanation:

First we need to find how many half lives 135 years is:

135 ÷ 64 = 2.109375

Now we divide 100% by 2 to the power of the number of half lives. This is how you calculate the percentage of the original amount left. If you have the original mass, you can substitute that in instead of 100%:

100 ÷ $2^{2.109375}$ = 23.1747390635

To 1 decimal place it is 23.2%