Difference Between Acid and Alkaline

Acid vs Alkaline

Acids and bases are two important concepts in chemistry. They have contradictory properties. Alkaline is a subset of bases, thus have all the basic characteristics. There are various methods to differentiate between acid and alkali which is described below.


Acids are defined in several ways by various scientists. Arrhenius defines an acid as a substance that donates H3O+ ions in the solution. Bronsted- Lowry defines an acid as a substance that can donate a proton. Lewis acid definition is far more common than the above two. According to it, any electron pair acceptor is an acid. According to the Arrhenius or Bronsted-Lowry definition, a compound should have a hydrogen and the ability to donate it as a proton to be an acid. But according to Lewis, there can be molecules, which don’t possess hydrogen, but can act as an acid. For example, BCl3 is a Lewis acid, because it can accept an electron pair. An alcohol can be a Bronsted-Lowry acid because it can donate a proton, however according to Lewis, it will be a base.

Regardless of the above definitions, we normally identify an acid as a proton donor. Acids have a sour taste. Lime juice, vinegar are two acids we come across at our homes. They react with bases producing water, and also they react with metals to form H2, thus increase metal corrosion rate. Acids can be categorized into two, based on their ability to dissociate and produce protons. Strong acids like HCl, HNO3 are completely ionized in a solution to give protons. Weak acids like CH3COOH are partially dissociates and give fewer amounts of protons. Ka is the acid dissociation constant. It gives an indication of the ability to lose a proton of a weak acid. To check whether a substance is an acid or not we can use several indicators like litmus paper or pH paper. In the pH scale from 1-6 acids are represented. An acid with pH 1 is said to be very strong and as the pH value increases, acidity is decreased. Moreover, acids turn blue litmus to red.


‘Alkaline’ is having alkali properties. Group 1 and group 2 elements, which are also known as alkali metals and alkaline earth metals are considered to be alkaline when they dissolve in water. Sodium hydroxide, potassium hydroxide, magnesium hydroxide, calcium carbonate are some of the examples. Arrhenius defines the bases as the substances that produce OH- in solutions. Above molecules form OH- when dissolved in water, therefore, act like bases. Alkaline solutions react easily with acids producing water and salt molecules. They show a pH value higher than 7 and turn red litmus to blue. There are other bases except alkaline bases like NH3. They also have the same basic properties.

What is the difference between Acid and Alkaline?

- Acids have a sour taste, bases have a bitter taste and soap like slippery feeling.

- Acid dissociation in a solution produce protons, and alkaline solutions produce hydroxide ions.

- Acids turn blue litmus to red, and alkaline solutions turn red litmus to blue.

- In a pH scale acids are indicated below 7, and alkaline are indicated above 7.