Question

How are basic salts formed?

Short answer

Answer: A basic salt is a chemical compound formed by the partial neutralization of a base by an acid, resulting in a salt that still contains some unreacted base. This makes it slightly basic in aqueous solutions. It forms through an acid-base reaction, where an acid donates a proton (H+) to a base, which accepts it. When the reaction is incomplete, a basic salt is produced, consisting of a cation from the acid and an anion from the base.

Step-by-step solution

1. Definition of Basic Salts

Basic salts are chemical compounds formed by the partial neutralization of a base by an acid. In other words, a basic salt is formed when a base reacts with an acid, but the reaction is not complete. As a result, basic salts still contain some unreacted base, making them slightly basic in aqueous solutions.

2. Formation of Basic Salts

Basic salts are formed through a type of chemical reaction called an acid-base reaction. In an acid-base reaction, an acid donates a proton (H+) to a base, which accepts it. When a base reacts with an acid incompletely, meaning not all the base molecules have accepted protons, a basic salt is produced. The resulting basic salt will have a positive ion (cation) from the acid and a negative ion (anion) from the base.

3. General equation for formation of basic salts

The general equation to represent the formation of a basic salt is: $$ AB + HX \rightarrow AH + BX $$ Here, AB represents the base, HX represents the acid, AH represents the basic salt, and BX represents the byproduct of the reaction.

4. Example of Basic Salt Formation

Let us consider the formation of a basic salt through the reaction of sodium hydroxide (NaOH) with hydrochloric acid (HCl): $$ NaOH + HCl \rightarrow NaCl + H_2O $$ In this reaction, sodium hydroxide (a base) reacts with hydrochloric acid (an acid) to form sodium chloride (NaCl) and water (H2O). Sodium chloride is a neutral salt, not a basic salt. However, if the reaction is incomplete and some sodium hydroxide remains unreacted, the resulting salt will be a basic salt. One example of a basic salt that could be formed in this situation is sodium bicarbonate (NaHCO3): $$ 2NaOH + H_2CO_3 \rightarrow Na_2CO_3 + 2H_2O $$ Here, sodium hydroxide reacts with carbonic acid (H2CO3) to form sodium carbonate (Na2CO3) and water. Note that in certain cases, the term "basic salt" is also used to refer to salts that can hydrolyze in water to produce a basic solution, such as sodium carbonate in the example above: $$ Na_2CO_3 + H_2O \rightarrow 2 NaOH + H_2CO_3 $$ In this case, sodium carbonate dissociates in water to produce a small amount of sodium hydroxide and carbonic acid, generating a basic solution.

Key concepts

Acid-Base Reaction

An acid-base reaction is a fundamental chemical process where an acid and a base interact with each other. In these reactions, an acid donates a proton (H+) to a base. This exchange of protons leads to the formation of water and a salt. The nature of the salt depends on how completely the reaction proceeds between the acid and base.

• Acid: Substance that donates protons.
• Base: Substance that accepts protons.
• Product: Typically results in the formation of water and a salt, which could be neutral, acidic, or basic.

Understanding these reactions is crucial because they form the basis for creating different types of salts, including basic salts. When the reaction is incomplete, some unreacted base remains, leading to the creation of a basic salt.

Partial Neutralization

Partial neutralization refers to a situation during an acid-base reaction where the acid and base react incompletely. Essentially, not all of the base or acid is used up in the process.
This happens because either:

• The amounts of acid and base are not equivalent.
• The acid or base has been added in excess.

In these cases, the reaction doesn't proceed to completion, leaving behind unreacted base (or acid). This leftover base causes the resulting salt to be slightly basic. This concept is fundamental when dealing with basic salts, as they are a product of such incomplete reactions.

Chemical Equilibrium

Chemical equilibrium occurs when the forward and reverse reactions proceed at the same rate. Here, the concentrations of reactants and products remain constant over time. For reactions involving acids and bases, reaching equilibrium doesn't mean that the reaction has stopped; rather, both the forward and reverse reactions continue to occur at equal rates, maintaining a steady state.
Interesting attributes of equilibrium include:

• It allows prediction of the concentration of different species at equilibrium.
• The equilibrium constant (K) can be used to describe the extent of the reaction.

In the context of basic salts, this means that despite the base's partial neutralization, both the unreacted base and the reacted components coexist in a stable ratio.

Hydrolysis

Hydrolysis is a pivotal concept where salts react with water to form either acidic or basic solutions. In the case of basic salts, the anion from the salt reacts with water, leading to the formation of hydroxide ions (OH-) which makes the solution basic.
Key points include:

• Sodium carbonate, a common basic salt, undergoes hydrolysis in water.
• This reaction produces a basic environment due to the formation of additional hydroxide ions.

Hydrolysis is why many salts, although appearing neutral upon initial formation, exhibit either acidic or basic properties when dissolved in water.

Sodium Bicarbonate Formation

Sodium bicarbonate, a typical basic salt, is formed through the partial neutralization of sodium hydroxide with carbonic acid. When sodium hydroxide (a strong base) doesn't fully react with the carbonic acid, the residual hydroxide leads to the formation of sodium bicarbonate, which is a weakly basic compound.
Steps involved in its formation:

• NaOH reacts with carbonic acid (H2CO3).
• Incomplete reaction leads to remains of basic sodium hydroxide.

The resulting compound, sodium bicarbonate, is not only important in baking and cleaning but also serves as a common example of how basic salts are produced through partial neutralization processes.