Question

What is the mass of 2K remaining in a 16-gram sample of 2K after 37.2 hours?

A) 1.0 g
B) 2.0 g
C) 4.0 g
D) 8.0 g

Answer 1

The mass of radioactive potassium remaining after three half-lives (assuming a half-life of 12.4 hours) will be 2 grams; halved successively from the original 16 grams.

Step-by-step explanation:

The student is asking about the remaining mass of potassium (which I believe is referred to as 2K, likely meaning potassium-40 isotope, which is radioactive) after a certain period has passed. This involves the concept of half-life, which is the amount of time it takes for half of a radioactive substance to decay. Since the half-life of potassium-40 is not given in the question, we can't determine an exact answer. However, if we assume that the half-life is 12.4 hours, a common value for potassium-40, after 37.2 hours (which is approximately three half-lives), the remaining mass would be found by halving the initial mass three times:

1. After the first half-life (12.4 hours): 16 g divided by 2 = 8 g
2. After the second half-life (24.8 hours): 8 g divided by 2 = 4 g
3. After the third half-life (37.2 hours): 4 g divided by 2 = 2 g

The remaining mass of 2K would be approximately 2 grams, which corresponds to option B.