LAWS OF CHEMICAL COMBINATIONS

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 law of multiple proportion , 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.