Bases are substances that react withacids and neutralise them. They are usually metal oxides, metal hydroxides, metal carbonates or metal hydrogen carbonates. Many bases are insoluble - they do not dissolve in water. If a base does dissolve in water, we call it an alkali.

Bases:

Bases are a class of chemical substances that have the ability to accept protons (H+) or donate a pair of electrons. They are commonly referred to as proton acceptors or electron pair donors. Bases are characterized by their bitter taste, slippery texture, and ability to turn litmus paper from red to blue. They play a crucial role in various chemical reactions and have numerous applications in industries, laboratories, and everyday life.

Properties and Examples:

- Bases are typically hydroxides of metals or ammonia (NH3).
- Many bases are soluble in water and produce hydroxide ions (OH-) when dissolved.
- Common examples of bases include sodium hydroxide (NaOH), potassium hydroxide (KOH), calcium hydroxide (Ca(OH)2), and ammonia (NH3).

Alkalis:

Alkalis are a subset of bases that specifically refer to bases that are soluble in water. The term "alkali" is often used interchangeably with "base," but it specifically denotes bases that are capable of producing hydroxide ions (OH-) when dissolved in water. Alkalis are typically strong bases and are known for their ability to neutralize acids.

Properties and Examples:

- Alkalis are bases that readily dissolve in water to form hydroxide ions.
- They have a high pH (greater than 7) and turn red litmus paper blue.
- Common examples of alkalis include sodium hydroxide (NaOH), potassium hydroxide (KOH), and calcium hydroxide (Ca(OH)2).

Difference between Bases and Alkalis:

1. Composition: Bases can include compounds that are not soluble in water, while alkalis specifically refer to bases that are soluble in water.

2. Hydroxide Ion Production: Bases may or may not produce hydroxide ions when dissolved in water, whereas alkalis always produce hydroxide ions.

3. Neutralization: Alkalis are specifically known for their ability to neutralize acids due to the presence of hydroxide ions. Bases, on the other hand, may or may not have this property.

4. pH Level: Alkalis have a higher pH (greater than 7) compared to bases, which can have varying pH levels.

5. Usage: The term "base" is more general and encompasses a wider range of chemical substances, while "alkali" is a more specific term used for bases that are soluble in water and exhibit certain properties.

In summary, all alkalis are bases, but not all bases are alkalis. Alkalis are a subset of bases that specifically refer to bases that are soluble in water and produce hydroxide ions. Bases, on the other hand, have a broader definition and can include compounds that may or may not be soluble in water and may or may not produce hydroxide ions.