Question

Element Z has a half-life of 20 minutes. In an events chain concept map tracing the nuclear decay of a 200g sample of element Z, would any of element Z remain after 160 minutes? If so, how much?

Answer 1

Radioactive decay expression is stated as:

N(t) = N(o) e^(-0.693t/t1/2)

N(t) = Amount remaining after time t, N(o) = Initial amount at t=0, t1/2 = Half-life.

This expression is of exponential type and thus there is an amount remaining at any given time.

At t = 120 minutes, the amount remaining can be calculated as follows:
Substituting for the values given;
N(160) = 200*e^(-0.693*120/20) = 3.13 g