In 1789, the French chemist, Antoine Lavoisier, who's credited as being another father of chemistry, originated the law of conservation of mass. Now, the law states that in a chemical reaction, no matter is created or destroyed, but instead changes form. In a chemical reaction, we're going to say that the compounds before the arrow, so in this case H2 and O2, would be our reactants, and those after the arrow, in this case, H2O, would be our products. According to Lavoisier, all other reactants are converted to product with nothing lost. So to think about it, we could say that originally at the beginning of the reaction, we have H2 and O2, and we're mixing them together. Their combined amount of both of them together, let's say it's a 100 grams. Well, according to the law of conservation of mass, nothing is truly lost. It's just converted from one form to another. So all 100 grams of my reactants should be converted entirely into the product. So at the end, I'd have exactly 100 grams of the product. All of this would be gone. All of this has been transformed into H2O. So what this tells me is that if you know the total mass of your reactants in the beginning, then they should equal the total mass of products that you create at the end. So this is an incredibly important idea when it comes to the law of conservation of mass. That'll connect to other ideas later on such as stoichiometry and solution chemistry. So just remember, when it comes to the law of conservation of mass, it helps us to determine eventually the amount of product we could potentially form.
Law of Conservation of Mass - Online Tutor, Practice Problems & Exam Prep
"In a chemical reaction, no matter is created or destroyed, but instead changes form."
Lavoisier's Conservation of Mass
Law of Conservation of Mass
Video transcript
According to Lavoisier, all reactants are completely converted into products.
Law of Conservation of Mass Example 1
Video transcript
In this example question, it asks how many grams of water vapor will form if 25 grams of hydrogen gas mixes with 12 grams of oxygen gas? Now, applying what we just learned about the law of conservation of mass, this isn't going to be too difficult. Because remember, it states that the mass, the total mass of reactants, will equal the total mass of products. Here we have the masses of the reactants which are 25 and 12, so when we add them together, that'll give us the total mass of the product that could potentially form. So the answer here would be 37 grams of the product. Now, if we want to follow the law and the rules for significant figures, technically, this has 3 significant figures, and this has 3 significant figures, so the better answer would be 37.0 grams of water vapor, which is just water as a gas. So just remember, when we're simply applying the law of conservation of mass, the amount of reactants equals the amount of products. Now, later on, when we go into more advanced forms of calculations with chemical reactions, we're going to see that it's not always true. In those cases, we'll learn new mechanics and new approaches to answer those particular types of questions.
Following the Law of Conservation of Mass, predict the minimum amount of nitrogen that will react with 50.0 grams of hydrogen to produce 92.5 grams of ammonia.
Nitrogen + Hydrogen → Ammonia
Predict the amount of oxygen gas that will remain after the reaction of 112.6 grams of calcium with 24.0 grams of oxygen.
