Question

Sodium Carbonate is a basic salt because it is a salt of _______
(A) Strong acid and Strong base
(B) Weak acid and Weak base
(C) Strong acid and Weak base
(D) Weak acid and Strong base

Answer 1

Hint: Sodium Carbonate is a product of the neutralisation reaction between Sodium Hydroxide and Carbonic acid. The formula of Sodium carbonate is $N{{a}_{2}}C{{O}_{3}}$.

Complete step by step answer:
Let us first look into Sodium Carbonate as a compound before analysing its nature so as to help us answer this question.
Sodium carbonate($N{{a}_{2}}C{{O}_{3}}$) also known as washing soda or soda ash, is a sodium salt of carbonic acid and is a rather strong and non-volatile base. It is commonly found in nature as a crystalline heptahydrate which readily decomposes to form a white powder, i.e. the monohydrate and possesses a cooling alkaline taste. This compound can usually be extracted from the ashes of many plants and is also produced artificially in large quantities from common salt.

Now with its properties in mind and with the knowledge that it is basic in nature, let us try and analyse the reactants which are used in its formation.
We can easily observe that Sodium Carbonate ($N{{a}_{2}}C{{O}_{3}}$)is the salt produced by the neutralisation reaction of the strong base which is sodium hydroxide ($NaOH$) by the weak acid which is carbonic acid (${{H}_{2}}C{{O}_{3}}$). When dissolved in a polar solvent such as water, it dissociates into its ions constituting a sodium metal ion ($N{{a}^{+}}$) and a carbonate ion ($C{{O}_{3}}^{2-}$). Since the Carbonate ion is the conjugate base of a weak acid, it is therefore a stronger base and reacts with water in the solution as follows:

\[C{{O}_{3}}^{2-}\text{ }+\text{ }2{{H}_{2}}O\to \text{ }{{H}_{2}}C{{O}_{3\text{ }}}+\text{ }2O{{H}^{-}}\]

As shown above, hydroxide ion is released into the solution making it more basic in nature.

Thus, we can conclude that the answer to this question is option (D).

Note: It is a general notion that the pH of salts is influenced by their acid and basic counterparts which came together to produce them. If both of them are equally powerful then a neutral salt is formed. In all other cases, the salt tilts itself towards either the acidic or basic side depending on which among them was stronger.