Acid Strength:

The strength of an acid considers to its capability or trend to lose a proton. There are extremely few strong acids. A strong acid is one that totally ionizes (dissociates) in water; other words, one mole of a strong acid HA dissolves in water yielding one mole of H⁺ and one mole of the conjugate base, A^-. Necessarily none of the non-ionized acid HA remains. In difference a weak acid just only partially dissociates, and at equilibrium both of the acid and the conjugate base are available in solution. Instances of strong acids are hydroiodic acid (HI), hydrochloric acid (HCl), perchloric acid (HClO₄), hydrobromic acid (HBr), nitric acid (HNO₃) and sulfuric acid (H₂SO₄). In water each of these necessarily ionizes 100%. The stronger an acid is, the more simply it loses a proton, H⁺. Two main factors which contribute to the easiness of deprotonation are the polarity of the H-A bond and the size of atom A, which ascertains the strength of the H-A bond. Acid strengths are as well frequently discussed in terms of the stability of the conjugate base.

Stronger acids have a larger K_a and a more negative pK_a as compared to the weaker acids.

Sulfonic acids that are organic oxyacids, are a type of strong acids. A general example is toluenesulfonic acid (tosylic acid). Not like the sulfuric acid itself, sulfonic acids can be solids. Actually, polystyrene functionalized into polystyrene sulfonate is a solid strongly acidic plastic which is filterable.

Superacids are acids that are stronger than 100% sulfuric acid. Instances of superacids are magic acid, fluoroantimonic acid, and perchloric acid. Superacids can eternally protonate water to provide ionic, crystalline hydronium "salts". They can as well quantitatively stabilize carbocations.