# What is an acid according to Arrhenius?

Jun 7, 2017

According the Arrhenius, an acid is such a compound which in an aquous solution releases proton (or ${H}^{+}$).

Such compounds must fulfill two criteria -

1) First, it must be soluble in water (even if it is partly soluble, that'll do but, total insolubility of a compound disqualifies it to be regarded as an Arrhenius acid).

2) Second, it must be able to donate ${H}^{+}$ in the solution.

Such acids may be classified as -

(a) Strong acids with a degree of dissociation $\alpha = 1$ which are almost completely dissociated.

Example - ${H}_{2} S {O}_{4} , H N {O}_{3} , H C l$

(b) Weak acids with a degree of dissociation $0 < \alpha < 1$ which are only partially dissociated but still donate ${H}^{+}$ to some extent in aquous solution.

Example - $C {H}_{3} C O O H , H C N , H C O O H$