10 Examples of Irreversible Reactions

An irreversible reaction is a chemical reaction that can only proceed in one direction. This means that the reactants can be converted to products, but the products cannot be converted back to reactants.

Rusting of iron and baking bread are very common examples of irreversible reactions. The reactions are often exothermic, releasing energy, and they cannot be easily reversed to regenerate the original reactants. These characteristics are key indicators of irreversible reactions.

Examples of Irreversible Reactions

Here are ten examples of irreversible reactions, along with explanations of why each is considered an irreversible reaction:

1.      Combustion of Hydrocarbons:

Reaction: CH₄ (Methane) + 2O₂ → CO₂ + 2H₂O

Explanation: When methane (CH₄) burns in the presence of oxygen (O₂), it irreversibly produces carbon dioxide (CO₂) and water (H₂O) along with the release of heat and light. This reaction cannot be easily reversed to recreate methane.

2.      Rusting of Iron:

Reaction: 4Fe + 3O₂ + 6H₂O → 4Fe(OH)₃

Explanation: Iron reacts with oxygen and water to form iron(III) hydroxide (Fe(OH)₃), a process known as rusting. This reaction is irreversible and leads to the corrosion and deterioration of iron and steel.

3.      Baking Bread (Yeast Fermentation):

Reaction: Glucose → Ethanol + Carbon Dioxide

Explanation: During bread-making, yeast ferments glucose to produce ethanol and carbon dioxide gas, causing the dough to rise. This reaction is irreversible and contributes to the texture and flavor of bread.

4.      Photosynthesis:

Reaction: 6CO₂ + 6H₂O + light energy → C₆H₁₂O₆ + 6O₂

Explanation: Photosynthesis is a complex, irreversible process in which plants convert carbon dioxide (CO₂), water (H₂O), and light energy into glucose (C₆H₁₂O₆) and oxygen (O₂).

5.      Digestion of Food (Enzymatic Reactions):

Reaction: Food + Enzymes → Absorbable Nutrients

Explanation: The digestion of food involves a series of irreversible enzymatic reactions that break down complex nutrients into smaller, absorbable forms for energy and growth.

6.      Decomposition of Hydrogen Peroxide:

Reaction: 2H₂O₂ → 2H₂O + O₂

Explanation: Hydrogen peroxide (H₂O₂) decomposes into water (H₂O) and oxygen (O₂) in an irreversible reaction, often catalyzed by enzymes like catalase.

7.      Formation of Sodium Chloride (Salt):

Reaction: Na + Cl₂ → 2NaCl

Explanation: The reaction between sodium (Na) and chlorine gas (Cl₂) to form sodium chloride (NaCl) is irreversible and results in the formation of common table salt.

8.      Polymerization of Plastics:

Reaction: Monomer Units → Polymer

Explanation: The polymerization of plastics involves irreversible chemical reactions where monomer units are linked together to form long-chain polymers. Once formed, it is challenging to reverse this process.

9.      Dissociation of Ionic Compounds:

Reaction: NaCl (s) → Na⁺ + Cl⁻ (in solution)

Explanation: Ionic compounds like sodium chloride (NaCl) dissociate into their constituent ions when dissolved in water. This process is irreversible as the ions remain separated in solution.

10.  Decomposition of Ammonium Nitrate:

Reaction: NH₄NO₃ → N₂O + 2H₂O

Explanation: Ammonium nitrate (NH₄NO₃) can decompose, producing nitrogen oxide (N₂O) and water (H₂O). This reaction is irreversible and can be used in industrial explosives.