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Chemical reactions are an essential part of technology, culture, and life itself. Many activities involving chemical reactions that have been known and used for thousands of years include burning fuels, smelting iron, making glass and pottery, brewing beer, and making wine and cheese.
Chemical reactions abound in Earth’s geology, the atmosphere and oceans, and a wide range of complex processes that occur in all living systems. Physical changes must be distinguished from chemical reactions. Changes in state, such as ice melting to water and water evaporating to vapour, are examples of physical changes. When a substance undergoes a physical change, its physical properties change, but its chemical identity remains unchanged. Water (H2O) is the same compound regardless of its physical state, with each molecule consisting of two hydrogen atoms and one oxygen atom.
When water, as ice, liquid, or vapour, comes into contact with sodium metal (Na), the atoms are redistributed, yielding the new substances molecular hydrogen (H2) and sodium hydroxide (NaOH). We can tell that a chemical change or reaction has occurred because of this.
The characteristics of a chemical reaction
- When two or more molecules interact and form a new product, this is referred to as a chemical reaction (s).
- Compounds that react to form a new compound known as a Reactant. Product refers to the compounds formed as a result of the reactant’s interaction.
- In a chemical reaction, the chemical change must occur concurrently with the physical change in the reaction, such as heat evolution or colour change.
- A reaction can occur when two atoms, ions, or molecules of reactants form a new bond by breaking old bonds, and no atom is destroyed or created, but a new product is formed.
- The rate of reaction is affected by several factors, including pressure, temperature, and reactant concentration.
Types of Chemical Reactions
Different types of chemical reactions are classified based on the formation of various types of products or changes in the condition of reactants.
- Combustion reaction
- Neutralisation reaction
- Decomposition reaction
- The Redox Reaction
- Precipitation or Double-Displacement Reaction
1. Combustion reaction
A combustion reaction is a type of chemical reaction that occurs between a fuel and an oxidant and results in a product known as an oxidised product. An oxidizer is a chemical fuel that must be burned, such as oxygen. In general, a reaction between a hydrocarbon and oxygen produces carbon dioxide, water, and heat.
Examples:
CH4 (g) + 2O2 (g) → CO2 (g) + 2H2O (g) + Heat
2Mg + O2 → 2MgO + Heat
2. Neutralisation reaction
A neutralisation reaction occurs when an acid and a base react to produce salt and water as byproducts. Water molecules are formed by the combination of OH– ions and H+ ions. When a strong base and a strong acid undergo a neutralisation reaction, the overall pH of the products must be 7. Consider the neutralisation reaction of hydrochloric acid (HCl) and sodium hydroxide (NaOH), which produces sodium chloride (Common Salt) and water.
Example:
HCl (l) + NaOH (aq) -> NaCl (aq) + H2O (l)
3. Decomposition reaction
A single component decomposes into two or more (multiple) products during the Decomposition reaction. To break the bond between reactants such as heat, electricity, light, and so on, a certain amount of energy is required.
Example:
The Decomposition of calcium carbonate (CaCO3) giving out CaO (Quick Lime) which are the major component of cement.
CaCO3 (s) CaO(s) + CO2(g)
The Calcium hydroxide (Slaked lime) on the decomposition gives Quick lime (CaO).
Ca(OH)2 CaO + H2O
The decomposition of salt (NaCl) gives Na and Cl as also products.
2NaCl →2Na + Cl2
4. Redox reaction
A reduction-oxidation reaction in which reduction (electronic gain) and oxidation (electronic loss) occur, resulting in the transfer of electronic species. Consider an electron-chemical cell-like redox reaction involving zinc and hydrogen.
Example:
Zn + 2H+ → Zn2+ + H2
In the above reaction, a zinc atom reacts with two positively charged hydrogen atoms, transferring electrons from the zinc atom and forming a stable molecule with a zinc ion as the product.
Oxidation – Oxidation is the process by which electrons are lost and the oxidation state of a given reactant increases.
Reduction – Reduction is an electron gain in which the reactant state of a given reactant decreases.
5. Single displacement reaction
More reactive metal displaces less reactive metal from its salt in this type of reaction. Products can be determined in these reactions via reactivity series. A reactivity series is a series in which the elements are arranged in decreasing order of reactivity. The elements at the top of the series are more reactive than the elements at the bottom of the series in this series.
Example:
2K + MgCl2→2KCl + Mg
Precipitation or Double-Displacement reaction
It is a type of displacement reaction in which two chemical species react and their ions, i.e. cations and anions, switch places, resulting in the formation of two new products. Examine the reaction between silver nitrate and sodium chloride now. After the double-displacement reaction, the products will be silver chloride and sodium nitrate.
Example:
AgNO3 + NaCl → AgCl ↓ + NaNO3
Conclusion
Chemical reactions are an essential part of technology, culture, and life itself. When two or more molecules interact and form a new product, this is referred to as a chemical reaction. In a chemical reaction, the chemical change must occur concurrently with the physical change in the reaction, such as heat evolution or colour change. Different types of chemical reactions are classified based on the formation of various types of products or changes in the condition of reactants. A combustion reaction is a type of chemical reaction that occurs between a fuel and an oxidant and results in a product known as oxidised product. When a strong base and a strong acid undergo a neutralisation reaction, the overall pH of the products must be 7. Direct combination, analysis reaction, single displacement, and double displacement are the four main types of reactions.
