Normality (N) in Chemistry:
Normality (N) is a measure of concentration in chemistry that expresses the number of equivalents of a solute per liter of solution. It is commonly used in acid-base reactions, redox reactions, and precipitation reactions.
Formula for Normality
N=(Number of gram equivalents)÷(Volume of solution in litres)
N = M ×Equivalent factor
where:
- M = Molarity (mol/L)
- Equivalent factor = The number of reactive species (H⁺, OH⁻, electrons, etc.) contributed by each molecule.
Normality in Different Contexts
Acid-Base Reactions:
- Normality depends on the number of H⁺ or OH⁻ ions a compound can donate or accept.
- Example: 1 M H₂SO₄ (sulfuric acid) is 2 N because each H₂SO₄ molecule donates 2 H⁺ ions.
Redox Reactions:
- Normality depends on the number of electrons transferred per mole of reactant.
- Example: 1 M KMnO₄ in acidic medium is 5 N because MnO₄⁻ gains 5 electrons per reaction.
Precipitation Reactions:
- Normality is based on the number of ions reacting in a precipitation reaction.
- Example: 1 M BaCl₂ is 2 N because it provides 2 Cl⁻ ions.
Advantages of Normality:
- Useful in titration calculations, as it directly relates to equivalents.
- Helps compare solutions based on their reactive capacity, not just molarity.
- Simplifies stoichiometric calculations in acid-base and redox reactions.
However, normality depends on the reaction context, making it less universal than molarity.
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