What is the meaning of the term ‘Base’?
In the field of chemistry, a ‘base’ can be defined as a substance that releases hydroxide ions when dissolved in aqueous media. Typically, basic substances have a bitter taste (especially alkalis) and are slippery to the touch. Other notable characteristics of bases include:
- They change the colour of red litmus paper to blue.
- They undergo chemical reactions with acidic substances to form salts.
- They typically accept H+ ions (or protons) from suitable donor compounds.
- They hold hydroxide ions that are either partially or completely displaceable.
When dissolved in water, bases reduce the hydrogen ion activity in the water by changing the autoionisation equilibrium of water (in which an equilibrium is established between water molecules, positively charged hydronium/hydrogen ions, and negatively charged hydroxide ions). Thus, the pH of water is effectively raised above the 7.0 mark when bases are dissolved in it.
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What are Alkalis? How are they Different from Bases?
Alkalis are bases that are soluble in water. Usually, the term ‘alkali’ is used to denote the ionic salts of alkaline earth metals or alkali metals that exhibit basic qualities. Therefore, it can be understood that alkalis form a subset of all bases. This implies that all alkalis are bases but all bases are not alkalis. It can also be noted that all alkalis adhere to the Arrhenius definition of basic substances (the Swedish scientist Svante Arrhenius defined bases as substances that cause an increase in the concentration of aqueous hydroxide concentration or a decrease in aqueous hydronium concentration when dissolved in water).
Some common examples of alkali salts are listed below.
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- Calcium hydroxide (Ca(OH)2)
- Magnesium hydroxide (Mg(OH)2)
- Sodium hydroxide(NaOH)
- Potassium hydroxide (KOH)
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It can also be noted that ammonia (NH3) is sometimes excluded from the alkali family despite the fact that it facilitates the formation of hydroxide ions when dissolved in water.
General Properties of Basic Substances
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- Typically, bases are bitter to the taste.
- Under standard conditions, the pH value of a basic solution is always greater than 7.
- Concentrated solutions of relatively strong bases (such as concentrated sodium hydroxide) are known to react with acidic substances in a violent manner. Such substances must, therefore, be stored with caution.
- Powerful bases are also known to have caustic effects on organic matter. Great care must be taken while handling such substances since accidental spillage on the skin can result in severe burns and permanent damage to the tissue.
- All basic substances have similar effects on certain chemical indicators. For example, all bases have the ability to turn red litmus blue. They are also known to impart a yellow colour to methyl orange and pink colour to phenolphthalein.
- In their molten or aqueous states, bases are great conductors of electric currents (since they dissociate into ions that increase the conductivity of the substance).
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Examples of Bases
A tabular column listing 10 examples of bases is provided below.
| Sl.No. | Name of the Base | Chemical Formula |
| 1 | Ammonia | NH3 |
| 2 | Calcium Hydroxide | Ca(OH)2 |
| 3 | Lithium Hydroxide | LiOH |
| 4 | Acetone | C3H6O (or) (CH3)2CO |
| 5 | Methylamine | CH3NH2 |
| 6 | Potassium Hydroxide | KOH |
| 7 | Magnesium Hydroxide | Mg(OH)2 |
| 8 | Pyridine | C5H5N |
| 9 | Sodium Hydroxide | NaOH |
| 10 | Zinc Hydroxide | Zn(OH)2 |
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Uses of Acids and Bases
Frequently Asked Questions on Base Meaning
What is the meaning of the term ‘base’ in chemistry?
Bases are defined as chemical substances that tend to donate electrons, release hydroxide ions (OH– ions), and/or accept protons (H+ ions) when dissolved in water. Some notable types of bases include Lewis bases, Bronsted-Lowry bases, and Arrhenius bases. Bases are known to increase the hydroxide ion activity or reduce the hydronium ion activity when they are dissolved in aqueous media. It is important to note that strong bases can react quite violently with acidic substances and can also cause damage to organic tissues. Therefore, strong bases must be handled and transported with the utmost care.
List some examples of strong bases.
Some examples of strong bases are, Lithium Hydroxide, Sodium Hydroxide, Potassium Hydroxide, Rubidium Hydroxide, Caesium Hydroxide, and Calcium Hydroxide
Bases typically have bitter tastes and soapy textures. The pH values of basic solutions are always above 7. Bases react with acids to form salts. Such a chemical reaction is called an acid-base neutralisation reaction. It can be noted that the pH of an aqueous solution of the salt formed from an acid-base neutralisation reaction is dependent on the strength of the parent acid and the parent base. For example, a strong acid and a weak base will typically yield an acidic salt and a strong base, when reacted with a weak acid, will often yield a basic salt.
What are monoacidic, diacidic, and triacidic bases?
- A monoacidic base is a base that produces one hydroxide ion when one of its molecules undergoes complete ionisation. Examples of such bases include potassium hydroxide and sodium hydroxide.
- A diacidic base is a base that produces two hydroxide ions when one of its molecules undergoes complete ionisation. Examples of such bases include magnesium hydroxide and barium hydroxide.
- A triacidic base is a base that produces three hydroxide ion when one of its molecules undergoes complete ionisation. Common examples of triacidic bases include iron (II) hydroxide and aluminium hydroxide
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