calculate the remaining mass, in grams, of Americium-241 used in a smoke detector after 2 000 years

Question

Use the information in the text to calculate the remaining mass, in grams, of Americium-241 used in a smoke detector after 2 000 years.

The initial mass is 0.0002g and Americanium-241 has a half-life of 432 years

Answer 1

Step 1: Find how many half lives 2000 years.

2000 years = 4.6 half lives, approximately 5 half lives

432 years/half life

Step 2: See how many grams remain after 5 half lives.

0.0002 g --> 0.0001 g--> 0.00005 g --> 0.000025 g--> 0.0000125 g --> 0.0000625 g