Laws of Chemical Combination Importent Definitions Chapter 1 Chemistry Class 11 Notes Chapter 1 Some Basic Concepts of

LAWS OF CHEMICAL COMBINATIONS:

Law of Conservation of Mass
It states that matter can neither be created nor destroyed.
Law of Definite Proportions
It stated that a given compound always contains exactly the same proportion of elements by weight.
Example :  Oxygen and hydrogen in water always bear ratio of  16:2 or 8:1 by mass
Law of Multiple Proportions
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 the other element, are in the ratio of small whole numbers.
Example
Hydrogen + Oxygen → Water
2g                 16g         18g
Hydrogen + Oxygen → Hydrogen Peroxide
2g                 32g          34g
Here, the masses of oxygen (i.e. 16 g and 32 g) which combine with a fixed mass of hydrogen (2g) bear a simple ratio, i.e. 16:32 or 1: 2.
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 same temperature and pressure.
Example
Hydrogen + Oxygen →     Water
100 mL         50 mL       100 mL
Thus, the volumes of hydrogen and oxygen which combine together (i.e. 100 mL and 50 mL) bear a simple ratio of 2:1
Avogadro Law
Avogadro proposed that equal volumes of gases at the same temperature and pressure should contain
equal number of molecules
Example .
Hydrogen + Oxygen →     Water
we see that two volumes of hydrogen combine with one volume of oxygen to give two volumes of water without leaving any unreacted oxygen.