If a substance has a half-life of 14.9 s, and there are initially 100.0 g of the substance, how many grams will remain after precisely five minutes?

[A] = 8.69x10⁻⁵g

Explanation:

Kinetics law of a radioactive atom, A, is:

Ln[A] = -kt + ln[A]₀

Where [A] could be taken as mass of A after time t (In seconds),

k is rate constant = ln2 / Half-Life

[A]₀ is intial mass of A

k = ln2 / 14.9s = 0.04652s⁻¹

Time in seconds:

5min * (60s / 1min) = 300s

Replacing each value:

ln[A] = -0.04652s⁻¹*300s + ln[100.0g]

ln[A] = -9.35

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