Chemical Kinetics — Chemistry STD 12 Science — Question
Maharashtra BoardEnglish MediumSTD 12 ScienceChemistryChemical Kinetics3 Marks
Question
Define and explain the term elementary reaction.
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Answer
Many reactions take place in a series of steps. Such reactions are called complex reactions. Each step taking place in a complex reaction is called an elementary reaction. This shows that a complex reaction is broken down in a series of elementary chemical reactions.
By adding all the elementary steps of a complex reaction we get the overall reaction.
The mechanism of a reaction is decided from the sequence of the elementary steps that are added to give overall reaction.
Elementary reaction : It is defined as the reaction which takes place in a single step and cannot be divided further into simpler chemical reactions.
The order and molecularity of the elementary reaction are same.
Some reactions take place in one step and cannot be broken down into simpler reactions. For example,
$\begin{aligned} & C _2 H _5 I _{( g )} \rightarrow C _2 H _{4( g )}+ HI _{( g )} \\ & O _{3( g )} \rightarrow O _{2( g )}+ O _{( g )}\end{aligned}$
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