Acids and bases are types of corrosive substances. The primary distinction is that substances with a pH value between 0 and 7 is an acid, and those with a pH value between 7 and 14 are considered bases. Acids and bases have different properties, and there have been three theories about them.

Theories of Acids and Bases

Arrhenius Theory of Acids and Bases: Svante Arrhenius came up with this theory in 1884. He states that acids produce H+ ions in aqueous solutions, and bases produce OH- ions. This theory only allows for aqueous solutions and hydroxide bases.

Bronsted-Lowry Theory: This theory states that in acid-base reactions, an acid releases a proton, and a base accepts it. This theory is broader, and it says that acids are proton donors, bases are proton acceptors, and bases beyond hydroxides are allowed. However, it only allows for protic acids. 

Lewis Theory of Acids and Bases: This model is the least restrictive. Rather than focusing on proton pairings, it focuses on electron pairings. It states that acids are electron-pair acceptors, and bases are electron-pair donors.

Properties of Acids

  • They taste sour.
  • They are corrosive.
  • They change litmus from blue to red.
  • Their water solutions conduct electric currents.
  • They react with bases to form salts and water.
  • They evolve H2 after a reaction with an active metal.

Some common acids are ascorbic acid, citric acid, vinegar, lactic acid, and carbonic acid.

Properties of Bases

  • They taste bitter.
  • They feel slippery.
  • They don’t change the color of litmus.
  • Their water solutions conduct electric currents.
  • They react with acids to form salts and water.

Some standard bases are detergent, soap, NaOH, and household ammonia.

Strong and Weak Acids and Bases

How strong or weak an acid is depends on its ability to dissociate their ions in water. A strong acid or a strong base will completely dissociate, whereas a weak acid or base will only partly dissociate. In fact, there are six known strong acids: hydrochloric acid, nitric acid, sulfuric acid, hydrobromic acid, hydroiodic acid, and perchloric acid. Strong bases are usually the hydroxides of Group I and Group II metals.