Question

The decomposition of vegetable into compost is an example _____ reaction
A.Exothermic
B.Endothermic
C.Displacement
D.None of the these

Answer 1

Hint: We know that exothermic reactions are those reactions, which gives out heat energy. Endothermic reactions are those reactions that absorb heat energy. Displacement reactions are those in which one atom is displaced by another atom.

Complete step by step answer:We can define displacement reactions as chemical reactions in which a reactive element displaces a least/less reactive element. We have to know that metals as well as nonmetals take place in a displacement reaction.
For example, consider the reaction between zinc and copper sulfate.
Based on the activity series, zinc is more reactive than copper. Hence, it would displace copper from copper sulfate solution. We can write this chemical reaction as,
\[CuS{O_4}\left( {aq} \right) + Zn\left( {aq} \right)\xrightarrow{{}}ZnS{O_4}\left( {aq} \right) + Cu\left( s \right)\]
Copper sulfate is reacted with zinc to form zinc sulfate and metallic copper.
We can define an exothermic reaction as a chemical reaction in which liberation of energy takes place in the form of heat (or) light. The change in enthalpy of exothermic reaction will be negative.
${\text{Reactant}}\xrightarrow{{}}{\text{Products + Energy}}$
Example of an exothermic reaction is the combustion reaction of methane. Methane reacts with oxygen to form carbon dioxide and water with the liberation of heat. We can write the chemical reaction as,
$C{H_4}\left( g \right) + {O_2}\left( g \right)\xrightarrow{{}}C{O_2}\left( g \right) + {H_2}O\left( l \right) + Heat$
We can define an endothermic reaction as a chemical reaction in which heat is absorbed from the surroundings to produce products. Majority of the physical processes are endothermic reactions as they don’t get involved in breaking or making chemical bonds.
${\text{Reactant + Energy}}\xrightarrow{{}}{\text{Product}}$
For example, Conversion of ice cubes to liquid water is an example of endothermic reaction because energy is absorbed from the surrounding by ice cubes and melts to form liquid water.
${H_2}O\left( s \right)\underset {} \leftrightarrows {H_2}O\left( l \right)$
The decay of vegetables into compost is an oxidative process. The decay of the matter leads to the production of carbon dioxide, oxides of nitrogen and sulfur, phosphates of magnesium, calcium, sodium and potassium chloride, water etc.
All these reactions liberate energy and hence, the net reaction leads to an increase in the liberation of heat. Therefore, the decomposition of vegetables into compost is an example of exothermic reaction.

And hence Option (A) is correct.


Note:
We can also remember that the decomposition of vegetable matter into useful compost is done by microbes. These reactions break down chemical bonds. The overall reaction is exothermic. But we cannot give a single chemical reaction as every vegetable matter is made up of various types of organic compounds and also the product produced that is a compost includes different composition of carbon to nitrogen ratio.