Question

Decomposition of ferrous sulphate is a/an:
(A) precipitation reaction
(B) exothermic reaction
(C) endothermic reaction
(D) synthesis reaction

Answer 1

Hint: Recollect the meaning of decomposition reaction. Start by writing the reaction which takes place during decomposition of ferrous sulphate. Determine what each term given the option is. Think about the reaction conditions in which decomposition of ferrous sulphate takes place.

Complete step by step solution:
- Decomposition reaction is a reaction in which one reactant decomposes in the presence of heat to form two or more simpler products.
- Let’s write the reaction when ferrous sulphate is decomposed.
- Ferrous sulphate decomposes in the presence of heat to form ferric oxide, sulphur dioxide and sulphur trioxide. The equation is given as,
\[2FeS{{O}_{4}}\xrightarrow{\Delta }F{{e}_{2}}{{O}_{3}}+S{{O}_{2}}+S{{O}_{3}}\]
- Let’s now take a look at the options.
- Precipitation reaction is the one in which two or more reactants react to form an insoluble stable solid compound called precipitate which settles down at the bottom of the reaction vessel. For example, potassium chloride reacts with silver nitrate to form silver chloride precipitate.
- Exothermic reaction is a reaction in which two or more reactants react with each other to form one or more products along with evolution of heat energy. Exothermic reactions are reactions in which heat is given out. For example, magnesium burns in air to form magnesium oxide and heat is released. All combustion reactions are exothermic. Basically, exothermic reactions are bond making reactions.
- Endothermic reaction is the opposite of exothermic reaction in which heat is absorbed to break the bonds. In endothermic reactions, heat from the surroundings is absorbed by the reactants to form products. Decomposition reactions require heat so they are endothermic reactions.
- Synthesis reactions are the reactions in which new compounds are manufactured or prepared using two or more reactants at specific reaction conditions. For example, Bosch- Haber process for synthesis of ammonia which involves reaction of nitrogen gas and hydrogen gas at extreme reaction conditions of high pressure and temperature to form ammonia.

- Therefore, decomposition of ferrous sulphate is an endothermic reaction.


Note: Remember bond-making processes are exothermic. Some exothermic processes are crystallization, combustion, etc. Bond-breaking processes are endothermic such as decomposition reactions. Precipitation reactions involve formation of insoluble products. Synthesis reaction is a manufacturing process.