9. A radioisotope has a half-life of 4.50 min and an initial decay rate of 8400 Bq. What will be

the decay rate after 18.0 min?

525 Bq

Explanation:

The decay rate is directly proportional to the amount of radioisotope, so we can use the half-life equation:

A = A₀ (½) ^ (t / T)

A is the final amount

A₀ is the initial amount,

t is the time,

T is the half life

A = (8400 Bq) (½) ^ (18.0 min / 4.50 min)

A = (8400 Bq) (½) ^4

A = (8400 Bq) (1/16)

A = 525 Bq