Molecular Mass
Molecular mass is a fundamental concept in chemistry that refers to the total mass of a molecule, calculated by summing the atomic masses of each element it contains, expressed in atomic mass units (u). This section expands on the earlier discussion of atomic mass and illustrates how to find the molecular mass of compounds through practical examples.
Key Concepts Covered:
- Definition: Molecular mass represents the mass of a molecule comprising two or more atoms, made by combining atomic masses based on the chemical formula.
- Calculation Method: The molecular mass is computed by adding together the atomic masses of all constituent atoms within the molecule.
- Example Calculation:
- For water (H₂O), the molecular mass is calculated as:
\[
(2 \times 1) + (1 \times 16) = 18 \text{ u}
\]
- For HNO₃ (Nitric Acid), the calculation considers:
\[
1 + 14 + (3 \times 16) = 63 \text{ u}
\]
- Formula Unit Mass: The concept of formula unit mass is introduced, applicable to ionic compounds, calculated similarly but using the unit formula instead of the molecular structure. An example is provided, such as the calculation for sodium chloride (NaCl).
Understanding molecular mass is crucial for various applications in chemistry, including stoichiometry, where it facilitates the calculation of reactants and products in chemical reactions. Overall, this section reinforces the significance of molecular mass in connecting the atomic structure and the macroscopic properties of matter.