Today we are going to discuss 5 laws of chemical combination. In a chemical
reaction, elements combine to form compounds and this combination of elements
is based on the 5 laws of chemical combination.
There are five laws of chemical combination
1.
Law of conservation of mass
2.
Law of definite or constant proportions
3. Law
of multiple proportions
4. Gay
Loussac’s law of gaseous volumes
5. Avogadro
law
If you are a class 9th student then you should
go through the following laws-
1. Law of
conservation of mass
2. Law of
definite or constant proportions
State the Law of Conservation of Mass
The law of conservation of mass states that mass can
neither be created nor destroyed.
The law of conservation of mass was given by Atonie Lavoisier.
The law of conservation of mass experiment
Lavoisier performed an experiment to prove the law of conservation
of mass
He performed an experiment by taking a weighed
quantity of mercury (II) oxide and heated it strongly.
Mercury (II)
oxide (red in colour) was decomposed into mercury and oxygen.
He weighed both mercury and oxygen and found that their
combined mass was equal to that of mercury oxide taken.
Then Lavoisier profound the law of conservation that in
every chemical reaction, the total masses of all reactants are equal to the masses
of all products.
State the law of Constant Proportion
The law of constant proportion states that the
proportion by mass of the elements that compose it are fixed, independent of
the origin of the compound or its mode of preparation.
The law of constant proportion was given by Joseph
Poust.
For example – In pure water, the ratio of the mass of hydrogen
to the mass of oxygen is always 1:8 irrespective of the source of water.
State
the Law of Multiple Proportions
The law of multiple proportions was given by Dalton. According
to this law if two elements can combine to form more than one compound, the
masses of one element that combine with a fixed mass of another element, are in the
ratio of small whole numbers.
Example
Hydrogen combines with oxygen to form two compounds –
water and hydrogen peroxide.
Hydrogen + Oxygen →water
2g + 16g 18
g
Hydrogen +
Oxygen →Hydrogen peroxide
2g + 32g 34g
The masses of oxygen (16g and 32g)combine with a fixed
mass of hydrogen (2g) bearing a ratio of 16:32 or 1:2.
State Gay Lussac’s Law of Gaseous Volumes
According to Gay Lussac’s law of gaseous volumes, when
gases combine or are produced in a chemical reaction they do so in a simple
ratio by volume provided all gases are at the same temperature and pressure.
Hydrogen +
Oxygen Water
100mL 50 mL
100mL
The volume of hydrogen and oxygen which combine has a
simple ratio of 2:1.
State Avogadro Law
According to Avogadro's law equal volumes of gases at the same temperature and pressure should contain an equal number of molecules.
Example
Two volumes of hydrogen combine with one volume of
oxygen to give two volumes of water without leaving any unreacted oxygen,
Related Topics
1. What happens during a chemical reaction
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