Introduction:
Sodium carbonate (Na2CO3) is a chemical compound commonly known as soda ash or washing soda. It is an important industrial chemical with various applications, including as a cleaning agent, pH regulator, and an ingredient in glass and paper production. In order to understand why sodium carbonate is considered a basic salt, we need to examine its chemical properties and the nature of its constituent ions.

Definition of a basic salt:
A basic salt is a compound that is formed from the reaction between an acid and a base. It contains a metal cation and a basic anion. When dissolved in water, a basic salt produces a solution with a pH greater than 7, indicating its basic nature.

Explanation:
Sodium carbonate is formed from the reaction between a weak acid, carbonic acid (H2CO3), and a strong base, sodium hydroxide (NaOH). The chemical equation for this reaction is as follows:

H2CO3 + 2NaOH -> Na2CO3 + 2H2O

Let's break down the reaction and analyze the properties of the resulting salt:

1. Carbonic acid (H2CO3): Carbonic acid is a weak acid that can partially dissociate in water. It is formed from the dissolution of carbon dioxide (CO2) in water. However, in the presence of excess water, carbonic acid readily decomposes into water and carbon dioxide gas. The dissociation equation for carbonic acid is as follows:

H2CO3 ⇌ H2O + CO2

As a weak acid, carbonic acid does not completely ionize in water, resulting in a low concentration of hydrogen ions (H+) in the solution. This contributes to the overall basic nature of the resulting salt.

2. Sodium hydroxide (NaOH): Sodium hydroxide is a strong base that completely dissociates in water, producing a high concentration of hydroxide ions (OH-). The dissociation equation for sodium hydroxide is as follows:

NaOH -> Na+ + OH-

The presence of a strong base in the reaction contributes to the overall basic nature of the resulting salt.

3. Sodium carbonate (Na2CO3): Sodium carbonate is the resulting salt of the reaction between carbonic acid and sodium hydroxide. It consists of two sodium cations (Na+) and one carbonate anion (CO3^2-). When sodium carbonate is dissolved in water, it dissociates into its constituent ions:

Na2CO3 -> 2Na+ + CO3^2-

The carbonate anion (CO3^2-) is a basic anion that can accept protons from water, resulting in the formation of hydroxide ions (OH-). This further contributes to the basic nature of the resulting solution.

Conclusion:
Based on the chemical properties of its constituent ions, sodium carbonate is considered a basic salt. It is formed from the reaction between a weak acid (carbonic acid) and a strong base (sodium hydroxide), resulting in a salt that can dissociate in water to produce hydroxide ions (OH-). This gives the resulting solution a pH greater than 7, indicating its basic nature.