The chemical formula and the gram formula are related concepts in chemistry, but they represent different ideas. The chemical formula describes the composition of a compound, while the gram formula mass refers to the mass of one mole of that compound.
Chemical Formula
- The chemical formula uses symbols and subscripts to show the types of atoms and their ratio in a molecule. For example, H₂O represents water, indicating two hydrogen atoms and one oxygen atom.
- It is a symbolic representation, showing the qualitative and quantitative aspects of a substance’s composition.
- The chemical formula does not provide any information about the mass of the compound.
Gram Formula Mass
- As the reference states, "Gram Formula Mass = mass of the solute/formula mass of the solute". It is always expressed in the unit grams/mole (g/mol).
- The gram formula mass is the molar mass of a compound, meaning it is the mass in grams of one mole of a particular substance. This mass is numerically equivalent to the formula mass.
- It is calculated by adding the atomic masses (from the periodic table) of all the atoms in the chemical formula and expressed in g/mol.
- For example, water (H₂O) has a gram formula mass of approximately 18 g/mol (2 x 1 g/mol for hydrogen + 1 x 16 g/mol for oxygen).
Key Differences Summarized
| Feature | Chemical Formula | Gram Formula Mass |
|---|---|---|
| Definition | Symbolic representation of a compound's composition | The mass of one mole of a compound |
| Information | Kind and ratio of atoms present | Mass in grams per mole (g/mol) |
| Purpose | Identifies a compound | Quantifies how much of the substance is present |
| Units | No specific unit | grams/mole (g/mol) |
| Calculation | Based on symbols and subscripts | Sum of atomic masses of all atoms in formula |
In essence, the chemical formula tells you what a compound is made of, while the gram formula mass tells you how much a specific quantity (one mole) of the compound weighs.
