* Empirical Formula: Represents the simplest whole-number ratio of atoms in a compound. It tells you the type of atoms present and their relative proportions.
* Molecular Formula: Represents the actual number of atoms of each element in a molecule of the compound.
Here's the key relationship:
* The molecular formula is always a whole-number multiple of the empirical formula.
Example:
* Glucose:
* Empirical Formula: CH₂O (This is the simplest ratio of carbon, hydrogen, and oxygen atoms)
* Molecular Formula: C₆H₁₂O₆ (This is the actual number of atoms in a glucose molecule)
To get from empirical formula to molecular formula, you need:
1. The empirical formula: This tells you the basic atom ratios.
2. The molar mass of the compound: This tells you the actual mass of a molecule.
Here's how to find the molecular formula:
1. Calculate the empirical formula mass: Add up the atomic masses of the atoms in the empirical formula.
2. Divide the molar mass of the compound by the empirical formula mass: This gives you the whole-number multiplier for the empirical formula.
3. Multiply the subscripts in the empirical formula by the multiplier: This gives you the molecular formula.
In summary:
* The empirical formula tells you the *type* and *relative number* of atoms in a compound.
* The molecular formula tells you the *actual number* of atoms in a molecule of the compound.
* The molecular formula is always a whole-number multiple of the empirical formula.
