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Chemical Reactions and Equations - Classify reactions: combination, decomposition, displacement, double displacement, and precipitation

Grade 10CBSE

Review the key concepts, formulae, and examples before starting your quiz.

πŸ”‘Concepts

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A Combination Reaction occurs when two or more reactants combine to form a single product. General form: A+B→ABA + B \rightarrow AB.

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A Decomposition Reaction is the opposite of combination; a single reactant breaks down into simpler products. It requires energy in the form of heat (Thermal), light (Photolytic), or electricity (Electrolytic).

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In a Displacement Reaction, a more reactive element displaces a less reactive element from its compound. Example: Fe(s)+CuSO4(aq)β†’FeSO4(aq)+Cu(s)Fe(s) + CuSO_4(aq) \rightarrow FeSO_4(aq) + Cu(s).

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Double Displacement Reactions involve an exchange of ions between two reactants to form two new compounds. These often result in the formation of a precipitate.

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A Precipitation Reaction is any reaction that produces an insoluble solid, called a precipitate, that settles out of the solution.

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A Neutralization Reaction occurs when an acid and a base react to form salt and water. Example: HCl+NaOH→NaCl+H2OHCl + NaOH \rightarrow NaCl + H_2O.

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Redox Reactions (Oxidation-Reduction) involve the transfer of oxygen or hydrogen. Oxidation is the gain of oxygen or loss of hydrogen. Reduction is the loss of oxygen or gain of hydrogen.

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Exothermic Reactions release heat to the surroundings, while Endothermic Reactions absorb heat from the surroundings.

πŸ“Formulae

CaO(s)+H2O(l)β†’Ca(OH)2(aq)+HeatCaO(s) + H_2O(l) \rightarrow Ca(OH)_2(aq) + \text{Heat}

2FeSO4(s)β†’Ξ”Fe2O3(s)+SO2(g)+SO3(g)2FeSO_4(s) \xrightarrow{\Delta} Fe_2O_3(s) + SO_2(g) + SO_3(g)

2AgCl(s)β†’Sunlight2Ag(s)+Cl2(g)2AgCl(s) \xrightarrow{\text{Sunlight}} 2Ag(s) + Cl_2(g)

Na2SO4(aq)+BaCl2(aq)β†’BaSO4(s)+2NaCl(aq)Na_2SO_4(aq) + BaCl_2(aq) \rightarrow BaSO_4(s) + 2NaCl(aq)

CuO+H2β†’Ξ”Cu+H2OCuO + H_2 \xrightarrow{\Delta} Cu + H_2O

πŸ’‘Examples

Problem 1:

Identify the substance oxidized and the substance reduced in the following reaction: MnO2+4HCl→MnCl2+2H2O+Cl2MnO_2 + 4HCl \rightarrow MnCl_2 + 2H_2O + Cl_2

Solution:

HClHCl is oxidized to Cl2Cl_2, and MnO2MnO_2 is reduced to MnCl2MnCl_2.

Explanation:

Oxidation is the removal of hydrogen; here HClHCl loses hydrogen to become Cl2Cl_2. Reduction is the removal of oxygen; MnO2MnO_2 loses oxygen to become MnCl2MnCl_2.

Problem 2:

What type of reaction occurs when silver nitrate solution is added to sodium chloride solution? Write the balanced equation.

Solution:

Double Displacement and Precipitation Reaction. Equation: AgNO3(aq)+NaCl(aq)β†’AgCl(s)↓+NaNO3(aq)AgNO_3(aq) + NaCl(aq) \rightarrow AgCl(s) \downarrow + NaNO_3(aq)

Explanation:

The silver (Ag+Ag^+) and sodium (Na+Na^+) ions exchange partners. The resulting silver chloride (AgClAgCl) is an insoluble white precipitate.

Problem 3:

Why is the decomposition of ferrous sulphate called a thermal decomposition reaction?

Solution:

It is called thermal decomposition because it requires heat energy to break down the reactant.

Explanation:

The reaction is represented as 2FeSO4(s)β†’Ξ”Fe2O3(s)+SO2(g)+SO3(g)2FeSO_4(s) \xrightarrow{\Delta} Fe_2O_3(s) + SO_2(g) + SO_3(g). The symbol Ξ”\Delta indicates that heat is supplied.

Classify reactions: combination, decomposition, displacement, double displacement, and…