What is Equivalent Weight?

In chemistry, equivalent weight (also known as gram equivalent) is the mass of one equivalent, that is the mass of a given substance which will combine with or displace a fixed quantity of another substance. It is a fundamental concept used in analytical chemistry to simplify calculations involving chemical reactions, especially in titrations and electrochemistry.

How to Use the Equivalent Weight Calculator

To use this tool effectively, follow these simple steps:

1. Enter Molar Mass: Input the molecular weight of the substance in grams per mole (g/mol). For example, the molar mass of Sulfuric Acid (H₂SO₄) is 98.07 g/mol.
2. Enter Valency Factor (n-factor): This is the number of reactive units. For acids, it is the basicity; for bases, it is the acidity; and for redox reactions, it is the number of electrons lost or gained.
3. Click Calculate: The tool divides the molar mass by the n-factor to give you the precise equivalent weight.

The Formula for Equivalent Weight

The mathematical representation is quite straightforward:

Equivalent Weight = Molecular Weight / Valency Factor (n)

Why is Equivalent Weight Important?

The concept of equivalents is vital when dealing with Normality. Unlike Molarity, which depends on the volume of solution, Normality measures the concentration of equivalent weights per liter. This is particularly useful in acid-base titrations where one equivalent of an acid always reacts with one equivalent of a base, regardless of the stoichiometry of the molecules themselves.

Frequently Asked Questions

Q: What is the n-factor for H2SO4?
A: For Sulfuric Acid, the n-factor is 2, because it can donate two hydrogen ions (H+).

Q: Can equivalent weight be the same as molar mass?
A: Yes, if the valency factor is 1 (like in HCl or NaOH), the equivalent weight is equal to the molar mass.