The half-life for a 100-gram sample of radioactive element X is 5 days. How much of element X remains after 10 days have passed?

Question

a
50 g
b
25 g
c
10o g - no change
d
12.5 g

Answer 1

The half-life of a radioactive substance is the time it takes for half of the substance to decay.

For element X, the half-life is 5 days. After 10 days (which is two half-lives), we can determine how much of the original 100-gram sample remains.

1. After the first half-life (5 days):

   • Remaining amount = \( \frac{100 \text{ g}}{2} = 50 \text{ g} \)

2. After the second half-life (another 5 days, totaling 10 days):

   • Remaining amount = \( \frac{50 \text{ g}}{2} = 25 \text{ g} \)

So, after 10 days, 25 grams of element X remains.

The answer is b) 25 g.