Difference Between Gram Molecular Weight and Gram Equivalent Weight

The key difference between gram molecular weight and gram equivalent weight is that the term gram molecular weight refers to the mass of a molecule in grams, which is numerically equal to the molecular weight of that substance, whereas the term gram equivalent weight refers to the mass of one equivalent in grams.

In brief, both gram molecular weight and gram equivalent weight are measured in the unit of grams. However, when considering these terms as molecular weight and equivalent weight, respectively, the unit of measurement can be any other unit of mass, e.g. kilograms.

CONTENTS

1. Overview and Key Difference
2. What is Gram Molecular Weight 
3. What is Gram Equivalent Weight
4. Side by Side Comparison – Gram Molecular Weight vs Gram Equivalent Weight in Tabular Form
5. Summary

What is Gram Molecular Weight?

Gram molecular weight is the mass of one mole of a compound equal in grams to the molecular weight. In other words, the gram molecular weight is the mass of a molecule in grams which is numerically equal to the molecular weight of that substance. Let us consider some examples to understand this term.

1. The molecular weight of one molecule of water is 18 g/mol. Therefore, the molecular weight of water in grams is 18 or, the gram-molecular weight of water is 18.
2. Similarly, the molecular weight of oxygen is 32 g/mol. Therefore, the gram molecular weight of oxygen is 32 grams.

In practice, the terms gram molecular weight and “mole’ have the same idea but they have different definitions because the term mole refers to the amount of a substance containing the same number of entities as the number of atoms in 0.012 Kg of the carbon 12 isotope.

What is Gram Equivalent Weight?

Gram equivalent weight is the mass of an equivalent in the unit of grams. This term describes the mass in grams of an element, group, or compound. However, this term is different from the term equivalent weight based on the unit of measurement. This is because the mass can be measured in different units, and an equivalent means any considered part of a material. Then we can express the mass of that part in the unit of measurement for the mass of that particular material, e.g. grams or kilograms mainly.

What is the Difference Between Gram Molecular Weight and Gram Equivalent Weight?

Gram molecular weight and gram equivalent weight are two important terms we use in general chemistry. The key difference between gram molecular weight and gram equivalent weight is that the term gram molecular weight refers to the mass of a molecule in grams which is numerically equal to the molecular weight of that substance, whereas the term gram equivalent weight refers to the mass of one equivalent in grams.

The following is a summary of the difference between gram molecular weight and gram equivalent weight in tabular form.

Summary – Gram Molecular Weight vs Gram Equivalent Weight

In summing up what we discussed above, the gram molecular weight and gram equivalent weight are two important terms that we commonly use in general chemistry. However, the key difference between gram molecular weight and gram equivalent weight is that the term gram molecular weight refers to the mass of a molecule in grams which is numerically equal to the molecular weight of that substance, whereas the term gram equivalent weight refers to the mass of one equivalent in grams.

Reference:

1. Helmenstine, Anne Marie. “What Is a Mole in Chemistry?” ThoughtCo, Aug. 27, 2020, Available here.

Image Courtesy:

1. “Analytical balance mettler ae-260” By US DEA –  (Public Domain) via Commons Wikimedia