1. Introduction to Salts
Salts are substances we use every day—common table salt is the best example. But in Chemistry, the word salt has a much broader meaning.
Salts are formed when acids react with bases, metals, or carbonates. They come in many types and have a wide range of uses in daily life and industries.
2. Scientific Definition of Salts
In Chemistry, a salt is a compound formed when the hydrogen ions \(H^+\) of an acid are replaced by metal ions or ammonium ions during a chemical reaction.
Most salts are made up of a positive ion (called a cation) and a negative ion (called an anion).
2.1. Formation of Salts
Salts are usually formed during a neutralisation reaction between an acid and a base. However, salts can also be formed by reactions of acids with metals, metal oxides, or carbonates.
2.1.1. Acid + Base → Salt + Water
This is the most common way salts are formed. It is called a neutralisation reaction.
\( \text{Acid} + \text{Base} \rightarrow \text{Salt} + \text{Water} \)
Example:
\( \text{HCl} + \text{NaOH} \rightarrow \text{NaCl} + \text{H}_2\text{O} \)
2.1.2. Acid + Metal → Salt + Hydrogen Gas
Some metals like zinc and magnesium react with acids to form salts.
\( \text{2HCl} + \text{Zn} \rightarrow \text{ZnCl}_2 + \text{H}_2 \uparrow \)
2.1.3. Acid + Carbonate → Salt + Water + Carbon Dioxide
Carbonates and bicarbonates react with acids to form salts and release carbon dioxide.
\( \text{Acid} + \text{Carbonate} \rightarrow \text{Salt} + \text{CO}_2 + \text{H}_2\text{O} \)
2.2. Nature of Salts
Depending on the strength of the acid and base used to form them, salts can be acidic, basic, or neutral in nature.
3. Properties of Salts
Salts show many characteristic properties depending on their chemical composition.
3.1. Physical Properties
- Salts are usually crystalline solids.
- They may be colourless or coloured.
- Most salts dissolve in water.
- Solid salts have high melting points.
3.2. Chemical Properties
- Salts in water dissolve to form ions.
- Some salts undergo hydrolysis (reaction with water) to form acidic or basic solutions.
- Many salts show characteristic colours in flame tests.
4. Types of Salts
Salts can be classified based on how they are formed and their pH nature.
4.1. Neutral Salts
Formed from a strong acid and a strong base. Their solution has pH = 7.
Example: \( \text{NaCl} \) (Sodium chloride)
4.2. Acidic Salts
Formed from a strong acid and a weak base. Their solution has pH < 7.
Example: \( \text{NH}_4\text{Cl} \) (Ammonium chloride)
4.3. Basic Salts
Formed from a weak acid and a strong base. Their solution has pH > 7.
Example: \( \text{Na}_2\text{CO}_3 \) (Sodium carbonate)
4.4. Double Salts
Contain more than one cation or anion.
Example: Mohr’s salt (Ferrous ammonium sulphate)
4.5. Complex Salts
Contain complex ions and are used in advanced chemistry.
Example: Potassium ferrocyanide
5. Common Examples of Salts
Some well-known salts used in daily life include:
- Table Salt (NaCl): Used in food.
- Baking Soda (NaHCO3): Used in cooking and cleaning.
- Washing Soda (Na2CO3): Used in detergents.
- Gypsum (CaSO4·2H2O): Used in construction.
- Epsom Salt (MgSO4·7H2O): Used in medicine.
6. Uses of Salts in Daily Life
Salts play a major role in households, industries, and biological systems.
- Table salt is essential for body functions.
- Washing soda is used in laundry.
- Baking soda helps in baking fluffy cakes.
- Gypsum is used in making plaster and cement.
- Salts are used in fertilizers and medicines.
7. Safety Precautions While Handling Salts
- Some salts are safe, but others may be corrosive—handle laboratory salts carefully.
- Wear gloves when dealing with strong or reactive salts.
- Store salts in labelled, airtight containers.
- Do not mix unknown salts, as dangerous reactions may occur.