Formula mass

Definition

Formula mass is the sum of the average atomic masses of all atoms represented in the chemical formula of a substance. It is typically expressed in atomic mass units (amu).

5 Must Know Facts For Your Next Test

1. Formula mass is calculated using the periodic table to find the atomic masses of each element in a compound.
2. The formula mass is used for ionic compounds, while molecular mass refers to covalent compounds.
3. To calculate formula mass, multiply the atomic mass of each element by the number of atoms of that element in the formula and then sum these values.
4. Formula mass helps in converting moles to grams and vice versa using molar mass.
5. It is essential for determining empirical formulas from experimental data.

Review Questions

• How do you calculate the formula mass of NaCl?
• What is the relationship between formula mass and molar mass?
• Why is it important to know the atomic masses of elements when calculating formula mass?

Related terms

Molar Mass:

The mass of one mole of a substance, usually expressed in grams per mole (g/mol).

Empirical Formula:

The simplest whole-number ratio of elements in a compound.

Atomic Mass Unit (amu): A unit of mass used to express atomic and molecular weights, defined as one-twelfth the mass of an atom of carbon-12.