Question

How much of a radioactive substance must be presented to decay to 80 grams in 12 years if the half-life of the substance is 7.6 years?

Answer 1

239 grams.

Explanation:

Half life t(1/2) = ln 2 / k

So 7.6 = ln 2 / k

k = ln 2 / 7.6 = 0 0901204

N = No e^-kt

So after 12 years

80 = No / e^(-0.0901204*12)

No = 80 / e^(-0.0901204*12)

= 239.

Answer 2

Radioactive in half life is 51gram

Explanation:

80grams:12years

X :7.6years

12x÷x=x

7.6×80÷12=51gram