College

Thallium-208 has a half-life of 3 minutes. How long will it take for 60.0 g of thallium-208 to decay so that 15.0 g of the thallium-208 remains?

A. 3 min
B. 6 min
C. 9 min
D. 11 min

Please explain how you got the answer.

Answer :

Answer:

The decay takes 6min

Explanation:

The decay of an isotope as Thallium-208 follows the equation:

ln[A] = -kt + ln[A]₀

Where [A] is amount of isotope after time t

k is decay constant = ln 2 / t(1/2)

[A]₀ is initial amount of the isotope

Replacing:

[A] = 15.0g

k = ln 2 / t(1/2) = ln 2 / 3min = 0.23105 min⁻¹

t = ?

[A]₀ = 60.0g

ln[A] = -kt + ln[A]₀

ln[15.0g] = -0.23105 min⁻¹*t + ln[60.0g]

-1.38629 = -0.23105 min⁻¹*t

6min = t

The decay takes 6min

Final answer:

Thallium-208 has a half-life of 3 minutes. It will take 30 minutes for 60.0 g of thallium-208 to decay to 15.0 g.

Explanation:

The half-life of Thallium-208 is 3 minutes, which means that in each 3-minute interval, half of the remaining thallium-208 will decay. To determine how long it will take for 60.0 g of thallium-208 to decay to 15.0 g, we can use the concept of half-life.

First, we need to determine how many half-lives it will take for the amount to decrease from 60.0 g to 15.0 g.

Since each half-life is 3 minutes, dividing the total time by the half-life will give us the number of half-lives: Number of half-lives = (total time) / (half-life) = (30 min) / (3 min) = 10 half-lives

So, it will take 10 half-lives, or 30 minutes for 60.0 g of thallium-208 to decay to 15.0 g.

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