* Empirical Formula: The empirical formula shows the simplest whole-number ratio of atoms in a compound. C₂H₅ is the empirical formula for several different molecules.
* Molecular Formula: The molecular formula shows the actual number of atoms of each element in a molecule.
To figure out the molecular formula, you need the molar mass of the compound.
Here's how it works:
1. Calculate the empirical formula mass:
* C: 2 atoms * 12.01 g/mol = 24.02 g/mol
* H: 5 atoms * 1.01 g/mol = 5.05 g/mol
* Total: 24.02 + 5.05 = 29.07 g/mol
2. Divide the molar mass of the compound by the empirical formula mass. This will give you a whole number (or close to a whole number).
3. Multiply the subscripts in the empirical formula by the number you calculated in step 2. This will give you the molecular formula.
Example:
Let's say the molar mass of the compound is 58.14 g/mol.
1. Empirical formula mass = 29.07 g/mol
2. 58.14 g/mol / 29.07 g/mol = 2
3. C₂H₅ * 2 = C₄H₁₀
Therefore, if the molar mass of the compound is 58.14 g/mol, the molecular formula is C₄H₁₀ (butane).
