Question

Cobalt-60 has a half life of 5.25 years. If you started with a 40 gram sample of pure cobalt-60, how many grams of cobalt-60 would remain after 10.5 years?

Answer 1

Answer:

10 gm

Explanation:

Given:

Cobalt-60 has a half life of 5.25 years.

Initial mass of the Cobalt = 40 grams

How much decayed after 10.5 years?

Solution:

The general equation for half life is given below.

$A=A_{0}(\frac{1}{2})^{\frac{t}{h}}$----------(1)

Where A = mass of the substance that remains undecayed.

$A_{0}$ = the initial mass of the substance.

t = time

h = half life

Now, we substitute all known value in equation 1.

$A=40(\frac{1}{2})^{\frac{10.5}{5.25}}$

$A=40(\frac{1}{2})^{2}$

$A=40\frac{1}{4}$

$A=\frac{40}{4}$

A = 10 gm

Therefore, the remaining cobalt-60 after 10.5 years is 10 gm.