Neutralisation Reactions and Salts - SS1 Chemistry Lesson Note

Neutralisation reactions and the formation of salts are fundamental concepts in chemistry, particularly in the study of acid-base chemistry. These reactions play a crucial role in various scientific disciplines, ranging from chemistry and biology to medicine and industry. We will delve into the chemistry behind neutralisation reactions, the formation of salts, and their significance in different fields:

 

Neutralisation Reactions:

Neutralisation reactions occur when an acid reacts with a base to form a salt and water. The general equation for a neutralisation reaction is:

 

                                                Acid + Base —-> Salt + Water

 

During the reaction, the hydrogen ions (H+) from the acid combine with the hydroxide ions (OH-) from the base to form water (H2O). The remaining ions combine to form an ionic compound called a salt.

 

Formation of Salts:

Salts are ionic compounds composed of positively charged ions (cations) and negatively charged ions (anions). In neutralisation reactions, salts are formed as a result of the combination of the cation from the base and the anion from the acid. The specific salt formed depends on the nature of the acid and base used in the reaction.

For example:

-       When hydrochloric acid (HCl), an acid, reacts with sodium hydroxide (NaOH), a base, the neutralisation reaction yields sodium chloride (NaCl) and water (H2O).

 HCl + NaOH -> NaCl + H2O

 

-       Similarly, when sulfuric acid (H2SO4) reacts with calcium hydroxide (Ca(OH)2), the neutralisation reaction forms calcium sulphate (CaSO4) and water (H2O).

H2SO4 + Ca(OH)2 -> CaSO4 + 2H2O

 

Significance of Neutralization Reactions and Salts:

Neutralisation reactions and the formation of salts have significant implications in various scientific disciplines:

 

-       Acid-Base Chemistry: Neutralisation reactions are fundamental in studying acid-base reactions and understanding pH balance. They provide a means to control and regulate acidity in chemical systems and biological processes.

 

-       Medicine and Pharmacy: Neutralisation reactions play a vital role in pharmaceutical formulations, particularly in the preparation of antacids to neutralise excess stomach acid and in the development of medications for various conditions.

 

-       Environmental Science: Neutralisation reactions are employed in treating acidic wastewater and neutralising acidic soil to restore ecological balance. They also help mitigate the harmful effects of acid rain on the environment.

 

-       Industry and Manufacturing: Neutralisation reactions are utilised in various industrial processes, such as metal plating, chemical synthesis, and wastewater treatment.

 

-       Food Science: Neutralisation reactions are involved in food preparation and preservation. For example, the use of acids and bases to adjust pH levels in food products and the neutralisation of acidic or basic ingredients.

 

Properties of Salts:

Salts possess distinct properties that arise from their ionic nature. Some common properties of salts include:

-       Crystalline Structure: Salts often form crystals with a regular geometric arrangement of ions.

 

-       High Melting and Boiling Points: Salts generally have high melting and boiling points due to the strong electrostatic forces between ions.

 

-       Solubility: The solubility of salts varies, with some being soluble in water while others are insoluble or sparingly soluble.

 

-       Electrical Conductivity: Salts in the molten state or when dissolved in water can conduct electricity due to the presence of ions that are mobile and able to carry electric current.

 

-       Colour: Salts can exhibit a wide range of colours, with some being colourless and others displaying characteristic hues due to the presence of transition metal ions.