Part A Technetium-99m has a half-life of 6.0 hours. Assume you started with 28 mg of technetium-99m and 24 hours have passed, which is equivalent to 4 half-lives. How much technetium-99m remains?

the answer is 303.15 or 303

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.