A rock is found to contain 2.2 grams of uranium-235, a radioactive isotope. If the rock has undergone 2.75 half-lives, what was the original amount of uranium-235 in the rock and how old is the rock

Question

Beckham Foley

Chemistry

27 December, 23:15

A rock is found to contain 2.2 grams of uranium-235, a radioactive isotope. If the rock has undergone 2.75 half-lives, what was the original amount of uranium-235 in the rock and how old is the rock

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Answers (1)

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Easton Andrews · Answer 1

=14.8 grams

Explanation:

The remaining amount is normally calculated using the formula:

Remaining mass = 1/2ⁿ * Original mass where n is the number of half-lives.

Therefore, original mass = Remaining mass * 2ⁿ

Remaining mass = 2.2 grams

Number of half lives = 2.75 half lives

Original mass = 2.2g * 2²·⁷⁵

=14.8 grams