LAWS OF CHEMICAL COMBINATIONS
Law of Conservation of Mass
(Given by Antoine
Lavoisier in 1789). It states that matter (mass) can neither be created nor
destroyed.
Law of Definite Proportions or Law of Constant Composition:
This law was
proposed by Louis Proust in 1799, which states that: 'A chemical compound
always consists of the same elements combined together in the same ratio,
irrespective of the method of preparation or the source from where it is
taken'.
Law of Multiple Proportions
Proposed by Dalton
in 1803, this law states that:
'When two elements
combine to form two or more compounds, then the different masses of one
element, which combine with a fixed mass of the other, bear a simple
ratio to one another'.
Gay Lussac’s Law of Gaseous Volumes
(Given by Gay Lussac in 1808.) According to this
law when gases combine or are produced in a chemical reaction they do so
in a simple ratio by volume provided all gases are at same temperature
and pressure.
e.g.H2(g) + Cl2(g)
---→2HCl(g)
1V 1V 2V
All reactants and products
have simple ratio 1:1:2.
Avogadro Law
(In 1811, Given by
Avogadro)
According to this
law equal volumes of gases at the same temperature and pressure should
contain equal number of molecules.
Dalton's Atomic Theory
All substances are made up of tiny, indivisible particles called atoms. Atoms of the same element are identical in shape, size, mass and other properties. Atoms of different elements are different in all respects.Atom is the smallest unit that takes part in chemical combinations. Atoms combine with each other in simple whole number ratios to form compound atoms called molecules. Atoms cannot be created, divided or destroyed during any chemical or physical change.
