An Erlenmeyer flask is placed on a digital scale with 10 grams of baking soda and 15 grams of vinegar. The scale reads 25 grams. The chemical reaction is allowed to finish, but the scale
now shows less mass than at the start. Why does this demonstration fail to show the law of
conservation of mass?

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.