Question

If three half-lives have passed since a scientist collected 100 grams of sodium-24, how much Na-24 is left now?

A. 0 grams

B. 24 grams

C. 50 grams

D. 12.5 grams

Answer 1

After three half-lives, 12.5 grams of Na-24 is left.

Step-by-step explanation:

To calculate how much sodium-24 (Na-24) is left after three half-lives, we need to understand the concept of half-life. Half-life is the time it takes for half of a radioactive substance to decay.

The half-life of sodium-24 is 15 hours.

Each half-life reduces the amount of Na-24 by half. So after the first half-life, there would be 50 grams left. After the second half-life, there would be 25 grams left.

And after the third half-life, there would be 12.5 grams left. Therefore, the correct answer is D. 12.5 grams.