During the quantitat studies of chemical changes,the combination of elements to form compounds is governed by some basic laws, these are known as Laws of chemical combination.
Law of conservation of Mass
This law establish the relationship between the masses of reactants and products during a chemical reaction. This law was postulated by A. Lavoisier in 1750.
This law statesDuring any physical or chemical change, the total mass of the products is equal to the total mass of the reactants.
Or
"Matter can neither be created nor destroyed during any physical or chemical change".
12g carbon combines with 32g oxygen to give 44g carbon dioxIde. This law may be explained with the help of Landolt's experiments.
Law of Conservation of Mass in the
Light of Modern Research
It is stated by modern research that mass can be converted into energy, There is some energy formed in each reaction, by which some mass has been lost.
According to Einstein, mass and energy are related as
E = mc2
where, m= the mass of substance, c = velocity of light(3x 108 m/s) and E = energy
But in chemical reactions energy released or absorbed is too less, hence, the change in mass (decrease or increase)taking place becomes negligible. These changes can be clearly seen in nuclear reactions.
Law of Constant Composition
This law was stated by French chemist Joseph Proust. This law states that
"A sample of a pure chemical compound always coniısts same elements combined together in the same detinite proportions by mass, whatever be its source"
e.g. it is tound by the analysıs of water (take from various places like river, falls and wells) that in each sample of water,
the ratio of hydrogen and oxygen is 2 : 16 or 1 : 8 by mass.
Law of Multiple Proportions
This law was proposed by John Dalton. It states that, An element may form more than one compound with another element. For a given mass of an element, the masses of other elements (in two or more compounds) come in the ratio of small integers.
e.g. in NH3, 14g of nitrogen requires 3 g of hydrogen and in hydrazine (N2H4) 14 g of nitrogen requires 2 g of hydrogen.
Hence, fixed mass of nitrogen required hydrogen in the ratio3:2 in two ditterent compounds (3 : 2 is a simple ratio). Thus,
this is in agreement with "law ot multiple proportions.
To be continue...🌺
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