Are there any chemical changes that do not obey the Law of Conservation of Mass?
No, there are no chemical changes that do not obey the Law of Conservation of Mass. This law applies to every chemical reaction, meaning matter can neither be created nor destroyed.
Antoine Lavoisier proposed that in every operation, an equal quantity of matter exists both before and after the operation. Therefore, the total mass of the reactants always equals the total mass of the products.
Sometimes, a mass difference may be observed if a product escapes. For example, when vinegar reacts with baking soda, carbon dioxide gas is formed. If the gas escapes into the air, the final mass seems less. However, if the reaction is contained, the initial and final readings match perfectly.
Explanation
The textbook context explicitly states that the Law of Conservation of Mass applies to every chemical reaction. It uses the example of vinegar and baking soda to explain that while an open setup might show a mass difference due to escaping gas, a closed setup (like a conical flask with a balloon) proves the total mass remains exactly the same before and after the reaction.