Question

Complete the following reactions and write the balanced equations:

$FeS{O}_4\left(s\right)\underset{Decomposition}{\overset{Heat}{\to }}$

$Pb{\left(N{O}_3\right)}_2\left(s\right)\underset{Decomposition}{\overset{Heat}{\to }}$

Answer 1

Decomposition reaction

Reactions in which a complex reactant breaks down into two or more simpler products are called decomposition reactions. Decomposition reactions can be considered as the opposite of combination reactions. A compound undergoes decomposition by absorbing energy in the form of heat, light or electricity and based on the source of energy, decomposition reactions are classified as thermal decomposition, photodecomposition and electrochemical decomposition.

The general form of a decomposition reaction is:

$AB\to A+B$

The given questions discusses the decomposition reactions of two compounds Ferrous sulphate and Lead nitrate. Therefore, the answer is divided into two parts. Part A discusses the decomposition of Ferrous sulphate and Part B discusses the decomposition of Lead nitrate.

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PART A

Decomposition of Ferrous sulphate

Decomposition of Ferrous sulphate (FeSO₄) is carried out by heating. When Ferrous sulphate crystals are heated, the water molecules escape from the crystal lattice forming anhydrous Ferrous sulphate. Anhydrous ferrous sulphate is decomposed by further heating to get Ferric oxide (Fe₂O₃), Sulphur dioxide (SO₂) and Sulphur trioxide (SO₃).

The balanced equation for the decomposition reaction is:

$2FeS{O}_4\left(s\right)\underset{Decomposition}{\overset{Heat}{\to }}F{e}_2{O}_3\left(s\right)+S{O}_2\left(g\right)+S{O}_3\left(g\right)$

(Ferrous (Ferric (Sulphur (Sulphur

sulphate) oxide) dioxide) trioxide)

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PART B

Decomposition of Lead nitrate

Lead (II) nitrate on heating decomposes into Lead monoxide (PbO), Nitrogen dioxide (NO₂) and Oxygen (O₂). Lead monoxide is a yellow solid and Nitrogen dioxide can be observed as reddish fumes escaping from the system.

The balanced equation for the decomposition is:

$Pb{\left(N{O}_3\right)}_2\left(s\right)\to PbO\left(s\right)+N{O}_2\left(g\right)+O_2\left(g\right)$

(Lead nitrate) (Lead (Nitrogen (Oxygen)

oxide) dioxide)