Types of Combination Reactions and Real-World Applications
Chemical reactions are crucial events in the universe. From the growing of a plant, the photosynthesis, ripening of fruit, and the final Decomposition of a plant, every stage is composed of a number of chemical reactions.
When coming to animals, their respiration, digestion, and reproduction are all accompanied by a chemical reaction. Hence a world without chemical reactions cannot be possible. There are several types of chemical reactions like decomposition reactions, disproportionation reactions, combination reactions, etc. This article is all about the combination reaction, types of combination reactions and combination reaction examples.
What is a Combination Reaction?
A combination reaction can generally be a chemical reaction where two or more elements or compounds combine to form a single products. Hence, we can say that a combination reaction occurs due to a combination of elements or compounds. Or combination reactions are reactions in which a single compound is formed due to a combination between two or more elements or compounds.
Hence a general combination reaction can be represented by the equation
A + B → AB. This is the equation of a combination reaction.
In combination reactions, there is no limitation in the number of reactants that can participate in the reaction. Also, the reaction is generally exothermic because, during a combination reaction, a new bond is formed between the reactant molecule that leads to the release of heat.
For example, the formation of the salt barium fluoride by the combination of barium metal and fluorine gas is a highly exothermic reaction.
Ba (s) + F2 (g) → BaF2 (s)
Cause of Chemical Combination
Elements or compounds combine together, and they form a product during a chemical reaction. What is the motive of this chemical combination? Or why do chemical combinations occur? The answer to this question is simple every element or compound take part in a chemical combination to attain stability. As per the lewis theory, an atom attains stability if it gains the noble gas configuration.
Hence, during a chemical reaction, electrons are shared between atoms, and they achieve a stable electronic configuration. Hence the tendency of an atom of various elements to attain stability by acquiring a noble gas configuration is the cause of chemical combination.
Types of Combination Reactions
There are 3 ways in which a combination reaction can take place.
Combination of two or more elements.
Combination of two or more compounds.
Combination of a compound with an element.
Let's look at each type in detail.
Combination of more than two elements: In this type, two or more elements combine together and form a single compound.
for example
Carbon and oxygen combine to form Carbon Dioxide gas
C (g) + O2 (g) → CO2 (g)
Hydrogen and oxygen combine to form water
H2 (g) + O2 (g) → 2H2O (l)
Combination reaction between two compounds: In this, two compounds combine together and form a new compound.
E.g. The formation of calcium hydroxide (slaked lime) by the reaction of calcium oxide (quick lime) and water.
CaO (s) + H2O(l) → Ca(OH)2 (s)
Combination reaction between a compound and an element: A compound reacts with an element and forms a new compound. Formation of Carbon Dioxide gas from the compound carbon monoxide and the element oxygen is an example of this type of combination reaction
2 CO(g) + O2 (g) → 2 CO2 (g)
Properties of Combination Reaction
In combination reactions, the number of reactants participating in the chemical reaction is not limited.
The product of a combination reaction between a metal and a non-metal is always an ionic solid.
e.g. Burning of magnesium in air and forming magnesium oxide.
Examples of Combination Reaction
Formation of magnesium carbonate from magnesium oxide and Carbon Dioxide
2MgO + 2 CO2 → 2 MgCO3
Formation of lithium sulphide from lithium and sulphur
Li + S2 → 2 LiS
Formation of ammonia from nitrogen and hydrogen
N2 + 3H2 → 2 NH3
Formation of ammonium sulphate from ammonia gas and sulphuric acid
2NH3 + H2SO4 → (NH4 )2 SO4
Key Features
Combination reactions are when two or more elements or compounds combine to form a new compound.
Combination reactions between two elements, two compounds or between an element and a compound are the three types of combination reaction.
Elements or compounds combine together to attain stability.
FAQs on Combination Reaction Explained: Concepts & Examples
1. What is a combination reaction? Explain with a simple example.
A combination reaction is a type of chemical reaction in which two or more reactants (which can be elements or compounds) combine to form a single product. The general form of this reaction is A + B → AB. For example, when magnesium ribbon is burnt in air, magnesium (Mg) combines with oxygen (O₂) to form a single compound, magnesium oxide (MgO). The balanced chemical equation is: 2Mg(s) + O₂(g) → 2MgO(s).
2. What are the main types of combination reactions based on the nature of reactants?
Combination reactions can be broadly categorised into three types based on the reactants involved:
- Combination of two elements: An element reacts with another element to form a new compound. Example: Carbon burning in oxygen to form carbon dioxide (C + O₂ → CO₂).
- Combination of an element and a compound: An element reacts with a compound to form a new, more complex compound. Example: Oxygen reacting with carbon monoxide to form carbon dioxide (2CO + O₂ → 2CO₂).
- Combination of two compounds: Two different compounds react to form a single new compound. Example: Calcium oxide (quicklime) reacting with water to form calcium hydroxide (slaked lime) (CaO + H₂O → Ca(OH)₂).
3. What are some common examples of combination reactions we see in daily life?
Many everyday processes are combination reactions. For instance, the rusting of iron is a combination reaction where iron combines with oxygen and water to form hydrated iron(III) oxide. Another common example is the use of quicklime (calcium oxide) for whitewashing walls. When mixed with water, it undergoes a combination reaction to form slaked lime (calcium hydroxide), which then reacts slowly with carbon dioxide in the air to form a shiny layer of calcium carbonate.
4. How is a combination reaction fundamentally different from a decomposition reaction?
A combination reaction and a decomposition reaction are essentially opposites of each other. The key difference lies in the number of reactants and products.
- In a combination reaction, two or more reactants join to form a single product (A + B → AB).
- In a decomposition reaction, a single reactant breaks down into two or more simpler products (AB → A + B).
Therefore, you can identify a combination reaction by seeing multiple substances on the left side of the equation and only one on the right.
5. Why do elements and compounds undergo combination reactions?
The primary driving force behind combination reactions is the quest for stability. Atoms or molecules combine to form new chemical bonds, which results in a new substance that is in a lower, more stable energy state than the original reactants. By forming a new compound, the constituent atoms often achieve a stable electron configuration, similar to that of a noble gas. This process typically releases energy, which is why many combination reactions are exothermic (release heat).
6. How can you identify a combination reaction just by looking at its chemical equation?
The most straightforward way to identify a combination reaction from its chemical equation is to examine the number of reactants and products. A reaction is a combination reaction if it has two or more reactants on the left side of the arrow and only one single product on the right side. For instance, in the equation N₂(g) + 3H₂(g) → 2NH₃(g), nitrogen and hydrogen are two reactants that form a single product, ammonia, clearly indicating a combination reaction.
7. Can a combination reaction also be classified as a redox reaction? Explain with an example.
Yes, many combination reactions are also redox reactions. A redox reaction involves the simultaneous oxidation (loss of electrons) and reduction (gain of electrons) of the reactants. For example, the formation of sodium chloride from sodium and chlorine (2Na + Cl₂ → 2NaCl) is a combination reaction. In this process, sodium is oxidised (loses an electron to become Na⁺) and chlorine is reduced (gains an electron to become Cl⁻), making it a perfect example of a redox reaction as well.
8. What is the importance of combination reactions in industrial processes?
Combination reactions are vital for producing many essential industrial chemicals. A prime example is the Haber-Bosch process, a combination reaction used to manufacture ammonia (N₂ + 3H₂ → 2NH₃), which is a key component of fertilisers worldwide. Another significant application is the production of sulphuric acid via the Contact process, which involves the combination reaction of sulphur dioxide and oxygen (2SO₂ + O₂ ⇌ 2SO₃). These products are fundamental to agriculture and numerous other manufacturing industries.
