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A chemical reaction is a process in which reactants react chemically and convert into products by chemical transformation. For example, Respiration – we inhale oxygen which reacts with glucose and produces carbon dioxide, water and energy. The reaction is given below.
C6H12O6 + 6O2 → 6CO2 + 6H2O + Energy
Characteristics of a Chemical Reaction
Chemical reactions show one or more than one of the following characteristics.
Evolution of gas
Change in colour
Change in temperature
Change in energy
Formation of precipitate
Change in state
Now understand these characteristics in detail.
Evolution of Gas – Some chemical reactions take place with the evolution of gas. For example, when zinc reacts with hydrochloric acid, hydrogen gas is evolved with the formation of zinc chloride.
Reaction - Zn + 2HCl → ZnCl2 + H2
Change in Colour – Some chemical reactions are accompanied by a change in colour. For example, when colourless lead nitrate reacts with potassium iodide, it forms a yellow precipitate of lead iodide and colourless potassium nitrate.
Reaction – Pb(NO3)2 + 2KI → PbI2 + 2KNO3
Colourless Colourless Yellow ppt colourless
Change in Temperature – Some chemical reactions are accompanied by a change in temperature. For example, some reactions are exothermic in nature, while some are endothermic.
Change in Energy – Chemical reactions often involve a change in energy. During a chemical reaction, energy can be evolved or be absorbed. For example, in combustion reactions, energy is released, such as the burning of a fuel.
Formation of Precipitate – Some chemical reactions are accompanied by the formation of the precipitate. For example, barium chloride reacts with sodium sulphate and forms sodium chloride and precipitate of barium sulfate.
Reaction – BaCl2 + Na2SO4 —> BaSO4 + NaCl
Precipitate
Change in State – Some chemical reactions are accompanied by a change in state. For example, ammonia gas reacts with hydrogen chloride gas and forms solid ammonium chloride crystals.
Reaction – NH3(g) + HCl(g) —-> NH4Cl(s)
Types of Chemical Reactions
Chemical reactions are of many types. Here, we are covering the most common eight types of chemical reactions, which are part of the class X chemistry syllabus as well.
Decomposition reaction
Combination reaction
Combustion reaction
Neutralization reaction
Single displacement reaction
Double displacement reaction
Precipitation reaction
Redox reaction
Decomposition Reaction – In a decomposition reaction, molecules or compounds break down into two or more than two simpler chemically new substances. For example, electrolysis of water. In the electrolysis of water, water breaks down into hydrogen and oxygen, which show completely different properties than water.
Reaction - 2H2O electricity → 2H2 + O2
Combination Reaction – In a combination reaction, two or more molecules are combined together chemically to form a new substance (compound). Combination and decomposition reactions are opposite of each other. For example, when we burn magnesium ribbon (or magnesium), it gives grey-black ash of magnesium oxide.
Reaction – Mg + O2 → MgO
Combustion Reaction – It is an exothermic reaction that releases energy, generally in the form of heat. It is a reaction between fuel and an oxidant (generally atmospheric oxygen) that produces smoke, water and heat generally. For example, when we burn methane, it gives carbon dioxide and water.
Reaction – CH4 + 2O2 → CO2 + 2H2O
Neutralization Reaction – In these reactions, acid and base react with each other and form salt and water. For example, hydrochloric acid reacts with sodium hydroxide (base) and forms sodium chloride (salt) and water.
Single Displacement Reaction – In these reactions, more reactive metal displaces less reactive metal from its salt. In these reactions, products can be determined through reactivity series. Reactivity series is a series in which elements are arranged in decreasing order of their reactivity. It means the elements present at the top of this reactivity series are more reactive than the elements present at the bottom.
The reaction of potassium with magnesium chloride is an example of a single displacement reaction. In this reaction, potassium displaces magnesium from its salt because potassium is more reactive than magnesium. Potassium is present at the top of the reactivity series and is the most reactive element.
Reaction – 2K + MgCl2 → 2KCl + Mg
Double displacement reaction – In these reactions, two aqueous ionic compounds exchange their ions (mostly cations) and produce two new compounds. For example, potassium nitrate reacts with aluminium chloride and forms aluminium nitrate and potassium chloride.
Reaction – KNO3 + AlCl3 ↔️ Al(NO3)3 + KCl
Precipitation Reaction – In these reactions, an insoluble precipitate is formed. In precipitation reactions, two soluble salts in aqueous solutions are combined and form an insoluble precipitate.
Reaction – AgNO3(aq) + KCl(aq) ↔️ AgCl + KNO3(aq)
Redox Reaction – Those chemical reactions in which oxidation and reduction take place simultaneously are called redox reactions. Oxidation is the addition of oxygen, while reduction is the addition of hydrogen (or removal of oxygen). We have already discussed oxidation and reduction in a separate article with the title ‘Oxidation and Reduction’. You can refer to this article for a detailed explanation of oxidation and reduction.
The reaction of copper oxide with hydrogen is an example of a redox reaction. In this reaction, hydrogen has undergone oxidation by gaining oxygen atoms while copper oxide has undergone reduction by removing oxygen.
List of Common Chemical Reactions
We are giving here a general list of common chemical reactions.
S.No. | Chemical reaction | Equation |
Electrolysis of water | 2H2O electricity→ 2H2 + O2 | |
Rusting of iron | 4Fe + 3O2 →2Fe2O3 | |
The reaction of quicklime (CaO) with water | CaO + H2O → Ca(OH)2 Ca(OH)2 is known as slaked lime. | |
Photosynthesis | 6CO2 + 6H2O → C6H12O6 + 6O2 (reaction takes place in the presence of sunlight and chlorophyll) | |
Respiration | C6H12O6 + 6O2 → 6CO2 + 6H2O | |
Combustion of hydrogen – Reaction of hydrogen gas with pure hydrogen. This is an exothermic reaction. | 2H2 + O2 → 2H2O + energy | |
Decomposition of FeSO4 | 2FeSO4 +heat → Fe2O3(s) + SO2(g) + SO3(g) (Fe2O3(s) is green in color) | |
Decomposition of lead nitrate – In this reaction, brown fumes of nitrogen dioxide gas are formed with the yellow coloured residue of lead oxide. | 2Pb(NO3)2 → 2PbO + 4NO2 + O2 | |
Displacement reaction of iron and copper sulfate – Iron is more reactive than copper, so it displaces copper from its salt and produces iron sulfate. | Fe + CuSO4 →FeSO4 + Cu |
This ends our coverage on a list of Various Types of Chemical Reactions. We hope you enjoyed learning and were able to grasp the concepts. We hope after reading this article you will be able to differentiate various reactions easily and it will help you in experiments as well because we have covered almost all-important chemical reactions of Class X Chemistry Experiments.