5) Nitrogen -16 has a half-life of 7.2 seconds. How much nitrogen -16 will remain in a 100 g sample in 21.6 seconds?

Here's how to calculate the remaining amount of Nitrogen-16:<br /><br />1. **Determine the number of half-lives:**<br /><br /> 21.6 seconds / 7.2 seconds/half-life = 3 half-lives<br /><br />2. **Calculate the remaining fraction:**<br /><br /> After each half-life, the amount of the substance is halved. So after 3 half-lives, the remaining fraction is (1/2) * (1/2) * (1/2) = 1/8<br /><br />3. **Calculate the remaining mass:**<br /><br /> (1/8) * 100 g = 12.5 g<br /><br />Therefore, 12.5 g of Nitrogen-16 will remain in the 100 g sample after 21.6 seconds.<br />