Eine radioactive isotope tritium decays with a first-order rate constant k of 0.056 year
What fraction of the tritium initially in a sample is still present 30 years later?

0.186 (18.6%)

Explanation:

The amount of mass of a radioactive isotope after a certain time t is given by the decay equation:

where

is the mass of the isotope at time t = 0

is the mass of the isotope at time t

is the decay constant of the isotope

t is the time

The equation can be rewritten as

Where the term on the left represents the fraction of isotope left after time t.

In this problem, we have:

is the decay constant of the isotope

We want to find the fraction of isotope left after time

t = 30 y

Substituting, we find:

while cooking a piece of 1/2 pound beef steak, a cast iron pan (2.4kg in weight) was heated 260 celsius.