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What are Bases? – Definition, Examples, Types, Properties and Uses

  • Last Updated : 03 Sep, 2021

Acids and bases are common compounds that interact to generate salt and water when they react with one another. Acid is derived from the Latin word acere, which means sour. Many chemicals that scientists refer to as acids are used in our daily lives. Citric acid is included in the orange or grapefruit juice you drink for breakfast (also known as Vitamin C). 

Lactic acid is produced when milk becomes sour. Any hydrogen-containing material capable of transferring a proton (hydrogen ion) to another chemical is classified as an acid. A base is a molecule or ion that can take a hydrogen ion from acid and accept it. Acidic substances are characterised by a sour flavour. An acid is a molecule that can contribute an H+ ion while also remaining energetically favourable after losing that ion. Blue litmus is known to become red when exposed to acids.

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  • Base compounds have a bitter flavour to them.
  • The texture of most bases is soapy.
  • When tested on litmus paper, it transforms red litmus paper into blue litmus paper in most cases.
  • In solution, the base compounds also conduct electricity.
  • When base compounds are dissolved in water, OH- ions are liberated.


NaOH, Ca(OH)2, Na2CO3, NH3, LiOH, KOH, CsOH, Ba(OH)2, RbOH, NaNH2, NaH, SiO2, Al2O3, MgO, CaO, LiCO3 on silica, KNH2 on alumina, BaO, BeO, KCN etc. 

Many examples of bases may be found in everyday life. Many common household items or chemicals, such as drain cleaning, detergent, lubricating grease, baking soda or baking powder, soaps, toothpaste, mouthwash, chewing gum, hair dye, insecticides, and so on, are actually bases.

Types of Bases:

Acidity, concentration, and degree of ionisation are three variables that can be used to classify bases.

  • Types of Bases Based on Acidity :

Acidity in bases is determined by the number of hydroxyl ions present. Based on acidity, bases are classified into three categories:

  1. Monoacidic Base
  2. Diacidic Base
  3. Triacidic Base
  • Monoacidic: Mono acidic bases are those that contain only one hydroxyl ion and interact with only one hydrogen ion. Mono acidic bases include NaOH, KOH, and others.
  • Diacidic: Di acidic base is a base with two hydroxyl ions that interact with two hydrogen ions. Ca(OH)2, Mg(OH)2, and other di acidic bases are examples.
  • Triacidic: Triacidic base is a type of base that comprises three hydroxyl ions and three hydrogen ions. Triacidic bases include Al(OH)3, Fe(OH)2, and others.
  • Types of Bases Based on Their Concentration in Aqueous Solution :

Based on their concentration in aqueous solution, bases are divided into two categories :

  1. Concentrated Base
  2. Diluted Base
  • Concentrated: The concentration of base in these types of bases is higher in the solution. Concentrated NaOH solution, for example.
  • Diluted: These types of bases have a lower concentration of base in their aqueous solution. For instance, dilute NaOH, dilute KOH, and so on.
  • Types of Bases Based on Their Degree of Ionization :

The degree of ionisation of bases in solution can be used to classify them. It’s also known as foundation strength. When dissolved in water, it produces a certain quantity of hydroxyl ions. The degree of ionisation distinguishes two types of bases.

  1. Strong Base
  2. Weak Base
  • Strong: A strong base is one that dissociates entirely or to a large extent in water. For instance, NaOH, KOH, and so forth.
  • Weak: A weak base is one that does not dissolve entirely or only dissociates to a very little level. For instance, NH4OH, and so on.

Properties of Bases:

  • General Properties of Bases:
  1. A hydroxide ion (OH–) is released into water by bases. The stronger the base becomes as more ions are released.
  2. Acids react with bases. When an acid and a base react, water and a compound known as a salt are formed.
  3. Bases turn a reddish-blue colour due to the presence of litmus.

A protein’s structure can be altered by bases. Bases have this quality, which makes them feel slick. Soap is a base that becomes incredibly slippery on your skin when wet. Because of their ability to modify the structure of proteins, some powerful bases are extremely hazardous.

Because human skin contains many proteins, strong bases that dissolve in water, such as lye, are particularly harmful. When these powerful bases come into contact with the skin, they begin to alter the skin’s structure. This can result in burns. To avoid skin harm, strong bases should be used with caution.

  • Physical Properties of Bases:
  1. Bases taste bitter- There are only a few alkaline food materials. It’s considerably more crucial to taste the bases with caution. Because of the ability of stronger bases to denturate protein, tasting bases is more harmful than tasting acids.
  2. Bases release a hydroxide ion in water solution.
  3. Bases neutralise acids in a neutralization reaction- The term “reaction” refers to the creation of water and salt when an acid and a base are combined. Where “Y” is the anion of the acid “HY” symbolically. The reaction is: ‘X’ is the cation of the base ‘XOH,’ and ‘XY’ is the salt in the result.  [ HY + XOH → HOH + XY ]
  4. Bases denature protein- This explains why your hands feel slick when you’re near a base. Strong bases that dissolve easily in water, such as sodium or potassium lye, are extremely harmful since protein makes up a large portion of the structural material of humans. The judicious use of strong bases can prevent serious flesh damage.
  5. Bases turn red litmus to blue- This isn’t to suggest that litmus is the only acid-base indicator available; it’s only that it’s the oldest.
  • Chemical Properties of Bases:
  • Reaction of Base with Metals: When alkali (base) reacts with metal, salt and hydrogen gas are produced.

                                                               Alkali + Metal → Salt + Hydrogen


  • When sodium hydroxide interacts with aluminium metal, sodium aluminate and hydrogen gas are generated.

2 NaOH + 2 Al + 2 H2O → 2 NaAlO2 + 2 H2

  • When sodium hydroxide interacts with zinc metal, it produces hydrogen gas and sodium zincate.

2 NaOH + Zn → Na2ZnO2 + H2

  • Reaction of Non-Metallic Oxides with Base: Salt and water are formed when non-metallic oxides react with a base.

                                                      Non-metallic oxide + Base → Salt + Water


  • Ca(OH)2 + CO2 → CaCO3 + H2O
  • Action of Alkalis/Base with Ammonium Salts: Ammonia is produced when alkalis react with ammonium salts.

                                            Alkali + Ammonium salt   →   Salt   +  Water  +  Ammonia


  • When calcium hydroxide reacts with ammonium chloride, calcium chloride water and ammonia are produced.

Ca(OH)2 + NH4Cl  →  CaCl2 + H2O + NH3

Uses of Bases:

  • Sodium hydroxide is used in the manufacture of soap and paper. The sodium hydroxide (NaOH) is also utilised in the production of rayon.
  • Bleaching powder is made from Ca(OH)2, commonly known as slaked lime or calcium hydroxide.
  • Calcium hydroxide is used to create dry mixtures for painting and decorating.
  • Magnesium hydroxide, popularly known as milk of magnesia, is a laxative that is extensively used. It is also used as an antacid since it decreases excess acidity in the human stomach.
  • In laboratories, ammonium hydroxide is a critical reagent.
  • Slaked lime can be used to neutralise any excess acidity in soils.

Sample Problems:

Question-1 What are bases?


  1. Base compounds have a bitter flavour to them.
  2. The texture of most bases is soapy.
  3. When tested on litmus paper, it transforms red litmus paper into blue litmus paper in most cases.
  4. In solution, the base compounds also conduct electricity.
  5. When base compounds are dissolved in water, OH- ions are liberated.

Question-2 What are the functions of bases?


At home, we employ bases as cleaning agents and antacids. Soaps, lye (which is used in oven cleansers), magnesia milk, and Tums are all examples of popular homemade bases. Each of them has a pH greater than seven, can consume free hydrogen, and neutralise acids.

Question-3 How do you determine the location of a base?


Count the hydrogens on each component before and after the reaction to determine if it is an acid or a basic. This product is acid when the amount of hydrogens decreases (donates ions of hydrogen). This material serves as the foundation when the amount of hydrogen in the atmosphere rises (accepts ions of hydrogen).

Question-4 What is the most important distinction between an acid and a base?


Acids and bases are two types of corrosive chemicals. Acidic materials have a pH value between 0 and 7, while bases have a pH value between 7 and 14. Acids are ionic chemicals that break down in water to create the hydrogen ion (H+).

Question-5 What are the physical properties of bases?


  • They have a bitter taste to them.
  • Their aqueous solutions have a soapy quality to them.
  • They change the colour of litmus paper from red to blue.
  • Their aqueous solutions are electrically conductive.
  • With the release of hydrogen gas, bases react with metals to generate salt.

Problem-6 What will happen when calcium hydroxide reacts with ammonium chloride?


When calcium hydroxide reacts with ammonium chloride, calcium chloride water and ammonia are produced.

Ca(OH)2 + NH4Cl  →  CaCl2 + H2O + NH3

Problem-7 What will happen when sodium hydroxide interacts with zinc metal?


When sodium hydroxide interacts with zinc metal, it produces hydrogen gas and sodium zincate.

2 NaOH + Zn → Na2ZnO2 + H2

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