Some Basic Concepts Of Chemistry (Tricks & Short Notes) For JEE & NEET

Some Basic Concept Of Chemistry 

Chemistry deals with the composition, structure and properties of matter. These expects can be tried and understood and term of basic constituents of matter: Atoms and Molecules. 

Chemistry is Divided In 4 Parts :-

The Chemistry is divided into Four Parts :

• Organic
• Inorganic 
• Physical 
• Analytical

Classification Of Matter

The Classification Of Matter is Based on the basis Of its Variation in Properties which is vary when an external forces is applied. 

The Matter is Classified into - 

• Physical Classification 
• Chemical Classification 

Now, the Physical Classification Further Divided into :-

• Solid
• Liquid
• Gas

And the Chemical Classification further divided into two parts :-

• Pure Substance 
• Mixtures

Base Quantity 

It is a Physical Quantity which cannot be defined in the term of Other Physical Quantity.  There are Seven Base Quantity - 

StoiChiometry [J.B. Richter (1789) ]

It is the Branch of Chemistry that Describes the Quantitative Relationship between Reactants and Products. 

StoiChiometry means Measurement Of Elements. 

Laws Of Chemical Combination

This Law Give us an Idea Of How the Elements reacts And Form Compound. 

There are Five Laws which is Given by Scientists after Many Experiments - 

1. Law of Conservation Of Mass :-

" Matter Can neither created nor destroyed during any chemical or physical change, however its physical or chemical nature may change. "

In case of nuclear reaction some of the mass is converted into energy as per -

  E = mc²

Mass Of Reactant = Mass Of Product

2 . Law of Constant Proportion:-

" It states that a chemical compound irrespective of the source it is obtained from, contains same elements combining in definite ratio by mass. "

Exception :-  Isotopes and Non-Stoichiometric Compounds. 

3 . Law of Multiple Proportions :-

" 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. "

4 . Law Of Gaseous Volumes:-

" In gaseous reaction, the reactants always combine in simple ratio by volume and form products, which is also form in simple ratio by volume at same temperature and pressure. "

This law is valid only for gaseous reactions. 

5 . Avogadro's Law:- 

" Equal volume of all gases contain equal number of molecules at same temperature and pressure. "

                  PV = nRT 

             =>   n = PV/RT

6. Law Of Reciprocal Proportions :-

"It states that If 3 Elements say A, B & C combine to form 3 different compounds AB, BC & AC, then the ratio of masses of A & B combining with the fixed mass of C is either same or simple multiple of the ratio in which mass of A & B combine with each other."

Atomicity:- 

Total no. Of atoms in a molecule.

1 amu = 1.66056 × 10-²⁴ g

Example -> He - 1 - MonoAtomic

Vapour Density :-

  Vapour Density (V.D.) = Density of Gas / Density Of H2

Molecular Weight = 2 × Vapour Density

Specific Gravity :-

Specific Gravity = Density of Substance / Density of Water

Molecular Mass :-

It is the Sum of Atomic Masses of the Elements in the molecules.

Atomic Weights Of Commonly Used Elements :-

H = 1 amu, He = 4 amu, O = 16amu, Na = 23 amu, Al = 27 amu, P = 31 amu, S = 32 amu, Cl = 35.5 amu, K = 39 amu, Ca = 40 amu, Fe = 56 amu. 

Mole Concept :-

A mole is the amount of substance that contains as many entities as there are in exactly 12 gram of C¹² isotopes.

No. Of Atoms in 1 mol of C¹² = 12g / 1.992648 × 10²³ atmos/mole

                                                    = 6.022×10²³ atoms/mole = Avagadro Number

Calculating No. Of Molez :-

Elements -   n = Given Weight / Atomic weight 

Compound -   n = Given Weight / Molecular Weight

For Gas -   n =  Given Vol at STP / 22.4