What is a gram equivalent?

A gram equivalent is the mass of a substance that reacts with or displaces a fixed amount of another substance. It is calculated as: Gram Equivalents = Mass / Equivalent Weight, where Equivalent Weight = Molecular Weight / n-factor.

n-factor (valence factor) depends on the substance type: for acids it's the number of replaceable H⁺ ions, for bases it's replaceable OH⁻ ions, for salts it's the total positive charge on cations, and for redox reactions it's the total change in oxidation state.

Why don't masses need to be equal in a reaction?

Because different substances have different molecular weights and different n-factors. What must be equal is the number of equivalents — the 'reacting power.' For example, 53g Na₂CO₃ (1 equivalent) reacts with 36.5g HCl (1 equivalent), even though the masses are different.

How is equivalent weight different from molecular weight?

Molecular weight is the mass of one mole of a substance. Equivalent weight is the mass that provides one equivalent of reacting power: Equivalent Weight = Molecular Weight / n-factor. For Na₂CO₃, MW = 106 g/mol but Eq.Wt = 53 g/eq because n-factor = 2.

PhysicalMediumNEET: 1-2 Q3D

Gram Equivalent — Why Masses Don't Match in Reactions

Stoichiometry & Mole Concept

Match the equivalents of Na₂CO₃ (n=2) and HCl (n=1) on a 3D balance, then hit 'Mix them!' and watch both sides react to nothing — even though one pan weighs 53g and the other just 36.5g. Equal equivalents react, unequal mass.

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Gram Equivalent — Why Masses Don't Match in Reactions

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Practice

Learned it? Now prove it under the clock.

How to use this lab