A widely used and well-known phrase about Lavoisier's Law is the one that says:
“In nature nothing is lost, nothing is created, everything is transformed"
In fact, this phrase was not proposed by the French chemist Antoine Lavoisier, but rather by the Greek philosopher Lucretius in the first century BC. This phrase is attributed to Lavoisier because the work of this scientist that led to the writing of the elementary treatise on Chemistry, in year 1774, consisted of carrying out several experiments in closed systems that proved the maintenance of mass in systems. chemicals.
During his study, Lavoisier noted that when a chemical reaction is processed in a closed system, the mass of the reaction reactants is exactly equal to the mass of the new materials formed at the end of the reaction. Thus, the famous weight law, called Lavoisier's law and which states:
“The sum of the masses of the reactants in a chemical reaction is equal to the sum of the masses of the products"
Reagent 1 Mass Product 1 Mass
+ = +
Reagent 2 Mass Product 2 Mass
Regardless of whether the reaction is taking place in an open or closed system, Lavoisier's Law is observed throughout the chemical process.
Whenever we develop calculations through Lavoisier's Law, we see that the mass maintenance of the system before and after the reaction is a constant. The atoms present in the reagents only undergo a reorganization, forming new substances (products).
You calculations involving Lavoisier's law indicate the mass that will be produced in the products and also the mass of any of the participants in the reaction. See some examples:
(UFGD) The chemical transformation:
2KI(s) + Pb (NO3)2 → 2KNO3(s) + PbI2(s)
white white white yellow
is an example of a reaction between solids that occurs quickly. In a glass container with a lid, weighing 20g, 2g of KI and 4g of Pb (NO) were placed.3)2, sprayed. The container, tightly closed, was vigorously shaken for the reaction to occur. What will the total mass of the vessel be at the end of the reaction?
Data provided by the exercise:
KI reagent mass = 2 grams;
Pb reagent mass (NO3)2 = 2 grams;
Mass of the container where the reaction takes place = 20 grams.
As the mass of the products is equal to the mass of the reactants, if we have 6 grams of the reactants (2+4), we will have a formation of 6 grams of products after the reaction, since the atoms in the products are the same in the reagents.
The total mass of the container will be the sum of the mass of the products (which is equal to that of the reactants) and the mass of the container.
2 + 4 + 20 = 26 grams
(UFGD) The transformation of ozone into common oxygen is represented by the equation: 2O3 → 3O2. When 96g of ozone is completely transformed, the mass of ordinary oxygen produced is equal to: Given: O=16u
a) 32g b) 48g c) 64g d) 80g e) 96g
According to Lavoisier's Law, the sum of the masses of the reactants is equal to the sum of the masses of the products. If we have 96 grams of ozone, the mass of oxygen produced will necessarily be equal to 96 grams.
(UNIFIED-RJ) According to Lavoisier's Law, when we do react completely, in an environment closed, 1.12g of iron with 0.64g of sulfur, the mass, in g, of iron sulfide obtained will be: Data: S=32; Fe=56
Fe + S → FeS
a) 2.76 b) 2.24 c) 1.76 d) 1.28 e) 0.48
The data provided by the exercise were:
Iron reagent mass = 1.12 grams;
Sulfur reagent mass = 0.64 grams.
Calculating the mass of FeS, which is the only product, according to Lavoisier's Law, we have to:
The sum of the masses of the reactants = the sum of the masses of the products
1.12 + 0.64 = x
x = 1.76 grams
By Me. Diogo Lopes Dias
Source: Brazil School - https://brasilescola.uol.com.br/quimica/calculos-envolvendo-lei-lavoisier.htm