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asambeis [7]
3 years ago
13

The half-life for a 400-gram sample of radioactive element X is 3 days. How much of element X remains after 15 days have passed?

Chemistry
1 answer:
Natalka [10]3 years ago
8 0

Answer:

The correct answer is - A. 12.5 gram.

Explanation:

Given:

The initial amount of sample = 400 gram

the half-life cycle = 3 days

after 15 days remain value = ?

Solution:

The number of half-lives in 15 days = 15/3

= 5 half-lives

the remaining amount of sample after one half-life 3 days = 400/2 = 200

the remaining amount of sample after 2nd half-life or 6 days= 200/2 = 100

the remaining amount of sample after 3rd half-life or 9 days= 100/2 = 50

the remaining amount of sample after 4th half-life or 12 days= 50/2 = 25

the remaining amount of sample after 5th half-life or 15 days= 25/2 = 12.5 gram

Thus, the correct answer is = 12.5 g.

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