Overview
This lecture explains the key difference between empirical and molecular formulas, describing what each type of formula represents and how to determine them.
Molecular Formula
- The molecular formula shows the actual number of each type of atom in a compound.
- Examples: Glucose (C6H12O6), Methane (CH4), and Hydrogen Peroxide (H2O2).
- Indicates the real atomic ratio present in the compound.
Empirical Formula
- The empirical formula is the simplest whole-number ratio of elements in a compound.
- To find the empirical formula, divide all subscripts in the molecular formula by their greatest common factor.
- Example: Glucose (C6H12O6) simplifies to CH2O as its empirical formula.
- Methane’s molecular and empirical formulas are both CH4 because it’s already simplified.
- Hydrogen peroxide (H2O2) simplifies to HO for its empirical formula.
Key Difference
- The molecular formula gives the actual count of atoms; the empirical formula gives the simplest ratio.
Key Terms & Definitions
- Molecular formula — the actual numbers of atoms of each element in a molecule.
- Empirical formula — the simplest whole-number ratio of elements in a compound.
- Subscript — the small number in a chemical formula showing the number of atoms of an element.
Action Items / Next Steps
- Review the molar mass and mole concepts if necessary.
- Practice simplifying molecular formulas to empirical formulas.