Open In App

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

Base is a chemical compound that consists of OH ions and accepts protons. Base in Chemistry are those compounds that turn red litmus blue and when reacted with acid they neutralize the reaction to give salt and water. The pH value of the base is greater than 7. Bases are bitter in taste and slippery in touch. The bases which are soluble in water are called Alkalis. Examples of Bases are Metal Oxides, Metal Hydroxides, etc. Soap is an example of a base that we use in daily life. In this article, we will learn about the definition, properties, and chemical reactions of Bases in detail.

Base Definition

Base is defined as the chemical compound whose pH value is greater than 7, accepts a proton, neutralizes acid, and turns red litmus to blue. They generally liberate OH ion on dissociation. Examples include NaOH, NaHCO3, etc. Following are some general features shown by the base:

Bases are one of the most important chemical compounds that are used in everyday life. Bases are used as an antacid to control acidity and in toothpaste to neutralize the bacterial action that produces acid in our mouth and prevents degradation of enamel and cavity. They are also used as baking powder, baking soda, and washing powder.

Lewis Base

Lewis Bases are the compounds that have electron pair and they can donate it to the compounds which are deficient in electron pairs. Lewis Bases are Nucleophilic in nature i.e., they are nuclei-loving which means they will attack a positively charged centre with their electron pairs. Examples of Lewis Base include Ammonia because in Ammonia (NH3) the centre atom Nitrogen has 5 electrons out of which 3 is used in making bonds with 3 Hydrogen atoms and one pair of electrons remains left with the N atom thus making NH3 a Lewis Base.

Arrhenius Base

According to Arrhenius’s Concept, Bases are compounds that release hydroxide ions when dissolved in water and increase the concentration of hydroxyl ions in the aqueous solution. For Example, when KOH is dissolved in water it will give OH ion and thus increase the concentration of OH in the water.

Bronsted Base

Bronsted Concept of Base is an advanced version of Arrhenius’s Concept which states that bases are compounds that accept H+ ion or proton to form their conjugate acid. For Example Cl is a base that accepts H+ to form HCl as its conjugate acid.

Types of Bases

Bases can be classified on the basis of acidity, concentration, and ionization ability. The classification is mentioned below

Types of Bases Based on Acidity

Acidity of a Base refers to the number of replaceable hydroxyl groups present in one molecule of the base. Based on acidity, bases are classified into three categories:

Monoacidic: Mono-acidic bases are those that contain only one replaceable hydroxyl ion and interact with only one hydrogen ion. Monoacidic bases include NaOH, KOH, and others.

Diacidic: Diacidic base is a base with two replaceable 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 replaceable hydroxyl ions and three hydrogen ions. Triacidic bases include Al(OH)3, Fe(OH)3, and others.

Types of Bases Based on Their Concentration in Aqueous Solution

Concentration refers to the amount of the base present in an aqueous solution. Based on their concentration in aqueous solution, bases are divided into two categories:

Concentrated Base: Concentrated bases are those in which the amount of base is large as compared to the solvent. Concentrated NaOH solution, for example.

Diluted Base: These types of bases have a lower concentration of base in their aqueous solution. Dilution is the process of reducing the percentage of a solute by adding more amount of solvent. For instance, dilute NaOH, dilute KOH, and so on.

Types of Bases Based on Degree of Ionization

Degree of ionization refers to the ability of a chemical compound to liberate their constituent ion when dissolved in water. In the case of Base, the degree of ionization refers to the ability of the base to release OHions when they are dissolved in water. Based on the degree of ionization, bases are classified into two types:

Strong Base: Strong Bases are those bases that dissociate completely and liberate OH- ion when dissolved in water. Some examples of Strong Bases include NaOH, KOH, etc.

Weak Base: The bases which don’t undergo complete dissociation and liberate only a fraction of OH- ion is called Weak Base. Examples of Weak bases include Al(OH)3, Cu(OH)2, etc.

Learn More, Strong and Weak Bases

Properties of Bases

As we know that bases are chemical compounds that have OH- ion, turn red litmus blue, etc. In this section, we will learn about the physical and chemical properties of Bases along with some brief knowledge of their general properties.

General Properties of Base

The general properties of Bases are mentioned below:

Physical Properties of Bases

Bases taste Bitter: Bases are bitter in taste. Due to its bitterness, we have only a few alkaline foods. There are only a few alkaline food materials. Bases need to be tasted with more caution as compared to acids.

Bases are Slippery in Touch: When touched Bases feel slippery. For Example soap.

Bases release OH Ion: When bases are dissolved in water they release hydroxyl ion(OH). Depending on the ability to liberate hydroxyl ions they are classified as Strong and Weak.

Bases neutralize Acids: When Bases react with acids, they neutralize each other and produce salt and water. This reaction is called Neutralization Reaction. Let’s say we have the acid “HY” and the base ‘XOH,’ then the salt formed will be ‘XY’. The equation for this reaction can be given as HY + XOH → HOH + XY.

Bases Denature Protein: Denaturation of Protein means the destruction of the stability and structure of the protein. This makes use of base harmful for humans as human skin and hair are made up of protein and when strong alkalis such as sodium or potassium hydroxide also called as Lye used they create a harmful impact on human skin.

Bases Turn Red Litmus to Blue: When bases are brought in contact with red litmus they turn it blue. However, it should be noted that no such change can be observed when we try to react dry base with red litmus paper. The Litmus Paper test is one of the oldest methods to test base. However, other indicators also exist such as Phenolphthalein

Bases Conduct Electricity: When bases are in solution form they have mobile OH- ion hence they can conduct electricity.

Chemical Properties of Bases

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

Non-metallic oxide + Base → Salt + Water

When Calcium Hydroxide, a base is reacted with Carbon Dioxide then Calcium Carbonate and Water is produced.

Ca(OH)2 + CO2 → CaCO3 + H2O

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

Examples of Bases

Bases generally are Metal Oxide, Metal Hydroxide, Metal Hydrogen Carbonate, Metal Carbonates etc. Let’s see some of the examples of bases with their application in tabular form:



Potassium Hydroxide KOH

Used in Alkaline Batteries

Sodium Hydroxide NaOH

Used in the manufacturing of soap and detergent

Magnesium Hydroxide Mg(OH)2

Used as antacids

Sodium Bicarbonate NaHCO3

Used as Baking Soda

Sodium Carbonate Na2CO3

Used as Washing Soda

Ammonia NH3

Used in the manufacturing of Cleaning and Pharma Products

Calcium Hydroxide Ca(OH)2

Used in White Washing

Uses of Bases

There are various use cases of base, some of these are:

Read More

FAQs on Bases in Chemistry

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.

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.

3. 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+) while Base dissociates to give OH- ion.

4. 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.

5. 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

6. What will happen when Sodium Hydroxide reacts with Zinc Metal?

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

2 NaOH + Zn → Na2ZnO2 + H2

7. What is Lewis Base?

Lewis Base are the compounds which donate a pair of electron to the electron deficient compound. Example includes NH3.

8. What are Bases made of?

Bases generally consist of OH ion. Apart from these metal oxides, carbonates and hydrogen carbonates are also bases.

9. What are Alkalis?

The bases which are soluble in water are called Alkalis. An example is Sodium Hydroxide NaOH.

10. What are Strong Base and Weak Base?

The bases which dissociate completely to give OH ion on dissolving in water are called Strong Base. Examples include NaOH. Weak bases are those which doesn’t dissociate completely to liberate OH ion is called a weak base. Examples of Weak Bases include Ammonium Hydroxide.

Article Tags :