21.5 Uses of Radioisotopes

How can a radioactive nuclide be used to show that the equilibrium:
$\text{AgCl} \left(s\right) \rightleftharpoons \text{Ag}^{+} \left(a q\right) + \text{Cl}^{−} \left(a q\right)$
is a dynamic equilibrium?

Iodine that enters the body is stored in the thyroid gland from which it is released to control growth and metabolism. The thyroid can be imaged if iodine-131 is injected into the body. In larger doses, I-133 is also used as a means of treating cancer of the thyroid. I-131 has a half-life of 8.70 days and decays by β⁻ emission.

(a) Write an equation for the decay.

(b) How long will it take for 95.…