The half-life of 32 grams of a radioactive substance is 6.5 hours. How many grams of the substance remain after 19.5 hours?
A)16 grams
B)8 grams
C)4 grams
D)2 grams
E)32 grams

Question

Quizplus · Accepted Answer

The half-life of a substance is the amount of time required for the substance to decay to half of its original mass. In the context of the question, 19.5 hours represents three half-lives. Therefore, the substance will be reduced to (1/2)3 or 1/8 its original mass. 1/8 x 32 gives the correct answer of 4 grams.

The Half-Life of 32 Grams of a Radioactive Substance Is