4 Basic Laws of Chemical Combination that You Should Know

law chemical combination
Chemistry can be defined as the study of composition, structure, properties of matter and the reaction by which one form of matter may be converted into another form. To understand the behavior of the combination of elements, you should know four basic laws of combination of elements.

Law of conservation of mass

This law was stated by Russian scientist Mikhail Lomonosov in 1756.

According to the law, the mass is neither created nor destroyed during the chemical combination of matter.

Consider a reaction of hydrogen and oxygen, we get water as the product.

Hydrogen + Oxygen → Water

According to the law, the sum of masses of reactants (hydrogen and oxygen) is always equal to the sum of masses of product (water).

Law of a definite combination

This law was stated by French chemist Joseph Proust. He was the first scientist to think that chemical compounds are formed from definite proportions.

The law stated that any pure compound always contains the same elements in a definite proportion by weight and irrespective of its source or method of preparation.

Joseph Proust did study copper carbonate to prove this law. He compared naturally occurred copper carbonate and artificial copper carbonate.

He found that proportions of copper, carbon, and oxygen of artificial copper carbonate were exactly identical to that of naturally occurring copper carbonate.

This law works well for stoichiometric compounds but fails with non-stoichiometric compounds.

Read also How to Determine Melting Point of a Substance

Law of multiple proportions

This law was stated by the British scientist who introduced atomic theory, John Dalton. This law was published in the first part of the first volume of the New System of Chemical Philosophy.

The law stated that if two elements chemically combine with each other forming two or more compounds with different compositions by mass then the rations of masses of two interacting elements in the two compounds are small whole numbers.

As we know carbon reacts with oxygen to form two compounds – carbon monoxide (CO) and carbon dioxide (CO2).

A fixed mass of carbon says 100 grams may react with 266 grams of oxygen to form carbon dioxide. On the other hand, carbon reacts with 133 grams of oxygen to form carbon monoxide.

The ratio of masses of oxygen that can react with carbon is 266:133 or you can say 2:1 which are small whole numbers.

This law works well for stoichiometric compounds but fails with non-stoichiometric compounds (compounds in which the proportion of elements cannot be represented by integers). Also, it does not work for polymers.

Gay Lussac’s law of combining volumes of gases

This law was stated by French chemist Joseph Louis Gay-Lussac. He studied numbers of gaseous reactions and discovered there is a definite relationship between volumes of gaseous reactants and that of gaseous products.
According to this law, when gases react together to produce gaseous products, the volumes of reactants and products bear a simple whole number ratio with each other, provided volumes are measured at the same temperature and pressure.
When 1 Litre of hydrogen and 1 Litre of chlorine react, 2 Litres of hydrogen chloride is formed, provided volumes are measured at the same temperature and pressure.
Hydrogen (1L) + Chlorine (1L) → Hydrogen Chloride (2L)
Hence the ratio of volumes is 1:1:2 which are the simple whole numbers.

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