Radioisotopes are often used in diagnostic imaging for detecting disease. The isotope 131I (iodine-131), which has a half-life of 8.02 days, is used in nuclear medical imaging. What percentage of the original activity in the sample remains after 17.5 days

Approximately 22.04% of the original.

Explanation: Radioisotopes, like iodine-131, have unstable nuclei. To become stable, they eject some particle (alpha or beta) or energy (gama).

Half-life is a time for half of the substance to decay. Activity is rate of decay, i.e., the number of decays per unit time.

Half-life and Activity are related by the following:

where

A is activity

is initial activity

n is number of half-lives passed in t

For iodine-131, half-live is 8.02, so in 17.5 it has passed:

n = 2.182

Final activity will be:

Which means after 17.5 days, there were 22.04% of the original iodine-101.

a. energy is absorbed in the reaction.

if in a given reaction the energy of products is greater than the energy of reactants it means that reaction is endothermic and during the reaction, the energy is absorbed by reactants. in an endothermic reaction, the products have more stored chemical energy than the reactants. and in this reaction the reactants are more stable than products before the compounds with less energy are always more stable.