Laws of chemical combinations

 1.Law of conversation of Mass:-

This law was given by Antoine Lavoisier (1743-1794).It states that matter can neither be created nor destroyed. 
                        This law was put forth by Antoine Lavoisier in1789.He performed careful experimental studies for combustion reactions for reaching to the conclusion. This law formed the basis for several later development in chemistry. Infact, this was the result of exact measurements of masses of reactants and products and carefully planned experiments performed by Lavoisier. 

2.Law of Definite Proportions :-

This law was given by ,a French chemist, Joseph Proust. He stated that a given compound always contains exactly the same proportion of elements by weight.It is sometimes also referred to as Law Of Definite Composition.

3.Law of Multiple Proportions :-

This law was proposed by Dalton in 1803 .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 combines with oxygen to form two components, namely water and hydrogen peroxide. 


4.Gay Lussac 's Law of Gaseous Volumes:-

This law was given by Gay Lussac in 1808.He observed that 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. 

5.Avogadro Law:-

In 1811,Avogadro proposed that equal volumes of gases at the same temperature and pressure should contain equal number of molecules. 


👉Significant Figures :-

Significant figures are meaningful digits which are known with certainty.The uncertainty is indicated by writing the certain digits and the last uncertain digit.

There are certain rules for determining the number of significant figures. These are stated below -

(a) All non-zero digit are significant. 
(b) Zeros preceding to first non-zero digit are not significant. 
(c) Zeros between two non-zero digits are significant. 
(d) Zeros at the end or right of a number are significant provided they are on the right side of the decimal point. 
(e) Exact numbers have an infinite number of significant figures. 


Stoichiometry And Stoichiometric Calculations :-

The word  'stoichiometry ' is derived from two Greek words - stoicheion ( meaning element)  and metron ( meaning measure). Stoichiometry, thus deals with the calculation of masses (some volumes also)  of the reactants and products involved in a chemical reaction. 

Or
The quantitative study of the reactants required or products formed is called stoichiometry. Using stoichiometry calculations, the amounts of one or more reactants required to produce a particular amount of product can be determined and vice -versa. The amount of substance present in a given volume of a solution is expressed in number of ways e. g., mass per cent, mole fraction, morality and molarity. 


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