An Arrhenius acid is any substance that ionizes when it dissolves in water to give the hydrogen ion or H+. Thus, the molecules of an acid can donate a proton or accept an electron pair in reactions.

Did you know: The word acid is derived from the Latin word meaning sour.

Types of acids

There are different types of acid. The first type of acid is the proton donor or the Bronsted acid. In the special case of acids protons donors form Hydronium ion H3O and are known as Arrhenius acids. Both these acids contain a hydrogen atom bonded to a chemical structure that is still energetically favourable after loss of H2.. 

Acids form aqueous solutions with a sour taste. An acid turns blue litmus red. It reacts with bases and certain metals to form salts. The aqueous solution of the acid has pH less than 7. A lower pH means a higher acidity and a higher concentration of positive hydrogen ions in the solution. Chemical and substances that show property of acid are called acidic.

Arrhenius acids when added to water increases the concentration of H+ ions in water. Acid base reactions involve the transfer of proton. 

Pure substances and solutions can be acids and can be derived from solids, liquids or gases. The secondary type of acids are Lewis acids which form a covalent bonds with an electron pair. Thus Lewis acids accepts electrons from another species. They are referred to as electron pair acceptors.  


An Arrhenius base is defined as any substance that gives the hydroxide ion or OH-, when it dissolves in water.

Bases are substances that are slippery to touch and taste astringent. They turn red litmus paper blue. They react with acids to form salts. They accept protons from any proton donors and contain OH- ions. Bases produce hydroxide ions OH- in aqueous solution and are called Arrhenius bases. For this bases usually contain hydroxide in the formula. 

There are bases that do not contain hydroxide ion nevertheless react with water which result in the increase of the concentration of the hydroxide ion. For example ammonia and water produce ammonia and hydroxide. In this reaction ammonia is a base as it accepts a proton from the water molecule. This is due to its ability to form a bond with the proton as it has an unpaired pair of electrons. 

A soluble base is called an alkali if it contains and releases OH- i ions. Though basicity is not the same as alkalinity. It can be considered to be chemical opposite to be solids. This is because acids increase the concentration of hydronium in water and bases reduce this concentration. A reaction between an acid and the base is called neutralization.

Acids and bases examples

Examples of acids include hydrochloric acid, acetic acid, sulfuric acid, citric acid found in fruits. 
Examples of bases are the hydroxide of alkalies metals and alkaline earth metals. 

Quick facts about acids and bases

  • Acids turn litmus paper red. Bases turn litmus paper blue
  • Acids usually taste sour whereas bases taste bitter
  • Acids and bases can help neutralize each other
  • A Strong bases can be slippery and slimy feeling.

Examples of acids include proteins (made up of amino acids) and Vitamin C (ascorbic acid)
Example of bases includes Ammonia


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