Difference Between Bronsted Lowry and Arrhenius

Bronsted Lowry vs Arrhenius
 

Acids and bases are two important concepts in chemistry. They have contradictory properties. 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 they also 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. K_a 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.

Bases have a slippery soap like feeling and a bitter taste. They react easily with acids producing water and salt molecules. Caustic soda, ammonia, and baking soda are some of the common bases we come across very often. Bases can be categorized into two, based on their ability to dissociate and produce hydroxide ions. Strong bases like NaOH and KOH are completely ionized in a solution to give ions. Weak bases like NH₃ are partially dissociated and give fewer amounts of hydroxide ions. K_b is the base dissociation constant. It gives an indication of the ability to lose hydroxide ions of a weak base. Acids with a higher pK_a value (more than 13) are weak acids, but their conjugate bases are considered as strong bases. To check whether a substance is a base or not we can use several indicators like litmus paper or pH paper. Bases show a pH value higher than 7, and it turns red litmus to blue.

Other than the above characteristics we can identify acids and bases based on some other features. Acids and bases are defined in several ways by various scientists like Bronsted, Lewis and Arrhenius.

Bronsted Lowry

Bronsted defines a base as a substance that can accept a proton and acid as a substance that can give out a proton. Bronsted put forward this theory in 1923. At the same time, Thomas Lowry independently presented the same theory. Therefore, this definition is known as Bronsted-Lowry definition.

Arrhenius

Svante Arrhenius, a Swedish scientist, proposed his theory on acids and bases in late 1800s. According to the Arrhenius definition, a compound should have a hydroxide anion and the ability to donate it as a hydroxide ion to be a base. And a compound should have a hydrogen and the ability to donate it as a proton to be an acid. So HCl is an Arrhenius acid and NaOH is an Arrhenius base. This theory helps to explain the water formation during an acid-base neutralization reaction.