Acid- Those subtances which gives H (positive) ions after dissolving in water . (Acid ve subtance hote hai jo pani me gholne par H positive ions dete hai ) Example - CH3COOH (acetic acid ), HCOOH(farmic acid ),HCl (hydrochloric acid ) ,H2SO4 (sulphuric acid ) ,HNO3 ( nitric acid ) Note - jo acid jitna adhik H ions deta hai wah utna hi jyada acidic hota hai . For example - H2SO4 water me dissolve hone par 2 H ions deta hai aur HCl water me dissolve krne par kewal 1 H ions deta hai ,bcoz H2SO4 jyada yani ki 2 H ions deta hai isiliye ye HCl se jyada acidic hoga ."agar same concentration hoga to ." Note 1 - those acid which completely dissolve in water means 100% solubility ,those acid known as strong acid . Example - H2SO4 ,HCl Note 2 - Those acid which is not completely dissolve in water known as weak acid . Example - CH3COOH ,HCOOH. Base - those subtances which gave OH negative ions after dissolving in water . (Ve subtance jo water me dissolve krne par OH negative ions det