I'm having problems to decide whether a substance is acidic or basic(organic and inorganic both)and lewis principle

							
Definitions for Acids and Bases 

        An  ACID is a compound that forms ions in solution and whose formula starts with “H”, and a  BASE is a compound that forms ions in solution and whose formula ends with “OH”.
The following properties can be used to help identify an acid or a base.
A substance is an ACID if it

      (a) conducts electricity when dissolved in water, and

      (b) reacts with a base, and

      (c) turns litmus paper RED*, and

      (d) reacts with magnesium or zinc to produce hydrogen gas, and

      (e) tastes sour.
A substance is a BASE if it

      (a) conducts electricity when dissolved in water, and

      (b) reacts with an acid, and

      (c) turns litmus paper BLUE*, and

      (d) feels slippery, and

      (e) tastes bitter.
     A substance that is neither an acid nor a base is said to be a NEUTRAL substance.
  NOTE :  There are only three types of solutions: acidic, neutral and basic. There is only one neutral

solution. However, there is a wide range of acidic solutions, from highly acidic to very slightly acidic. (A

“very slightly acidic” solution is almost neutral.) Similarly, there is a wide range of basic solutions, from

highly basic to very slightly basic. (A “very slightly basic” solution is almost neutral.)!!!!!






						

							Lewis base is a substance that has lone pair of electrons which it is capable of donating to others...

Acid is vice versa..
						

							
Hi Bhavin,



       A substance will be acid if it is capable of giving H+ ions.

Ex-H2SO4, HCl, HNO3. These all have H+ ions which they can give in water. So they are acids (Arrhenius Concept).



      Besides, there are some more compounds which can be called as acids. For example, AlCl3, BF3. The reason is an acid is also a substance which can accept lone pair of electron through a dative bond. You can see in BF3, octet of Boron is not complete. So it is in hunt for a pair of electrons. This is why it is an acid (Lewis Concept). 



       Similarly, if a substance has OH– ions, it is a base. Or if it can donate lone pair of electrons through a dative bond, we call it a base. For example, H3. It has a lone pair of electron on nitrogen atom which it can donate. This is the Lewis definition.



 Acid-Base Reaction



       H3N:                            -->           BF3



       Lewis base                                  Lewis acid



(since it is donating a                  (since it is accepting



Lone pair of electron).                  a lone pair of electron).