Question

The​ half-life of the radioactive element unobtanium-29 is 5 seconds. If 32 grams of unobtanium-29 are initially​ present, how many grams are present after 5 ​seconds? 10 ​seconds? 15 ​seconds? 20 ​seconds? 25 ​seconds?

The amount left after 5 seconds is ___ grams.

Answer 1

The amount of unobtanium-29 remaining after 5 seconds, which is one half-life, would be 16 grams. This is calculated by dividing the initial amount (32 grams) by 2 for each half-life that has passed.

Step-by-step explanation:

The half-life of a radioactive element is the time it takes for half of the original amount of the substance to decay. For unobtanium-29, which has a half-life of 5 seconds, we can calculate the amount of substance remaining after each half-life using the formula provided for radioactive decay:

• After 1 half-life (5 seconds): 32 grams / 2 = 16 grams
• After 2 half-lives (10 seconds): 16 grams / 2 = 8 grams
• After 3 half-lives (15 seconds): 8 grams / 2 = 4 grams
• After 4 half-lives (20 seconds): 4 grams / 2 = 2 grams
• After 5 half-lives (25 seconds): 2 grams / 2 = 1 gram

So, after 5 seconds, the amount of unobtanium-29 left would be 16 grams.