Why is a water bath used to evaporate the water from the copper sulphate solution instead of heating the evaporating basin directly with a Bunsen burner?

increased stability in the completion of fluorine's outer shell.

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.