Question

Suppose the half-life of element k is 20 minutes. if you have a 200 g sample of k, how much of element k will be left after 60 minutes? (do not use significant digits in answering this question).

A) 25 g
B) 50 g
C) 200 g
D) 100 g

Answer 1

After three half-lives (60 minutes) of element K, which has a half-life of 20 minutes, only 25 g of the original 200 g sample would remain.

Step-by-step explanation:

To determine how much of element K will be left after 60 minutes, given that its half-life is 20 minutes, we can apply the concept of half-life, which tells us that the quantity of a substance decreases by half every half-life period. For a 200 g sample:

• After the first 20 minutes (1 half-life), 100 g remains.
• After 40 minutes (2 half-lives), 50 g remains.
• After 60 minutes (3 half-lives), 25 g remains.

Therefore, the answer is 25 g of element K will be left after 60 minutes.