How to find n-factor for disproportionation reaction in such rxns where n1 is zero (n1 is change in oxidation no. of 1 )?

To determine the n-factor for a disproportionation reaction, we follow a systematic approach. When n₁ (change in oxidation number of one species) is zero, it usually means that particular species is not undergoing oxidation or reduction, but we still need to evaluate the overall reaction.

Understanding Disproportionation Reactions:
A disproportionation reaction occurs when the same element in a substance undergoes both oxidation (increase in oxidation number) and reduction (decrease in oxidation number).

The n-factor for a disproportionation reaction is given by:

n-factor = Total change in oxidation number per molecule / Number of reacting atoms of the element undergoing disproportionation

Case When n₁ = 0:
If n₁ = 0, it means that one oxidation state remains unchanged, and we focus only on the oxidation and reduction processes occurring simultaneously in the reaction.

Identify the element undergoing disproportionation.
Determine its oxidation states before and after the reaction.
Calculate the oxidation number change for the oxidation half.
Calculate the oxidation number change for the reduction half.
Sum the absolute values of these changes.
Divide by the number of atoms of the element participating in disproportionation.
Example: Disproportionation of Cl₂ in NaOH
Consider the reaction:

Cl₂ + 2NaOH → NaCl + NaClO + H₂O

Step 1: Identify the Element Undergoing Disproportionation
Chlorine (Cl₂) is undergoing disproportionation.

Step 2: Determine the Oxidation States
Cl₂ in elemental form has oxidation state 0.
In NaCl, Cl has oxidation state -1 (reduction).
In NaClO, Cl has oxidation state +1 (oxidation).
Step 3: Calculate the Change in Oxidation Number
In NaCl, chlorine goes from 0 to -1 (change = -1).
In NaClO, chlorine goes from 0 to +1 (change = +1).
Since we consider absolute values: Total oxidation number change = |+1| + |-1| = 2.

Step 4: Find the n-factor
The number of chlorine atoms undergoing disproportionation = 1 per Cl₂ molecule (because Cl₂ has 2 atoms, and each undergoes a different process).
n-factor = Total oxidation number change / Number of atoms undergoing disproportionation
= 2 / 1
= 2.
Final Answer
When n₁ = 0, the n-factor is found by summing the absolute oxidation number changes and dividing by the number of reacting atoms involved in the disproportionation.

For Cl₂ → NaCl + NaClO, n-factor = 2.







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