Question

Name the scientists who gave
A.Law of conservation of mass
B.Law of constant proportion

Answer 1

In this question we will define the law of conservation of mass and law of constant proportion. We know that mass is an amount of a substance in a matter. Its SI is Kg and grams to measure small quantities. The law of conservation of mass is used in chemical reactions and law of constant proportion used in stoichiometry chemistry. As we know that one cannot calculate mass in open state so when mass is in a closed system it is conserved.

Complete step by step answer:
Now we discuss about the law of conservation of mass:
The basic principle of law of conservation of mass was explained by Antonie Lavoisier. It states that mass can neither be created nor destroyed. In a chemical reaction it means the mass of reactants in the beginning of reaction must be equal to the mass of products. For e.g. if we burn wood, its total mass before burning and after burning remains equal.
Now we can see the law of constant Proportion: it is also known as law of constant composition or law of definite proportion. It was explained by French chemist Joseph Proust. Therefore it is also known as Proust’s law. It states that elements in a given chemical compound remain in fixed ratio by mass. For e.g. Water molecules always have hydrogen and oxygen in the ratio of $1:8$ .

Note:
It should be noted that mass can change its state from solid to liquid or liquid to gas or solid to gas. Law of constant proportion is a type of chemical combination but some compounds show variation to this law. For e.g. $FeO$ has a ratio which varies from $0.85:1$ to $0.95:1$ . With the help of law of conservation of mass we can calculate the unknown masses. E.g. of law of conservation in daily life can be burning of candle, melting of ice to water and then to vapours.