For ionic compounds: Compound formula is the same as the empirical formula. The compound formula defines the formula unit, the simplest whole-number ratio of positive and negative ions giving an electrically neutral unit.
name Empirical Formula Molecular Formula water H2O H2O aluminum chloride AlCl3 AlCl3 ethene CH2 C2H4 glucose CH2O C6H12O6
Empirical Formulas and mol: The empirical formula is the simplest whole-number ratio of numbers of mols of atoms in one mol of a compound. The mole (mol) is that quantity of matter possessing a mass equal to the formula weight expressed grams. For example:
Empirical formula of Copper Chloride: CuxCly
Cu (a monatomic element) H2O Al2O3 Atomic Wt.: 63.546 Formula Wt.: 18.016 Formula Wt.: 102. Mass of 1 mol = 63.546 g Mass of 1 mol = 18.016 g Mass of 1 mol = 102. g 63.546 g Cu/mol Cu 18.016 g H2O/mol H2O 102. g Al2O3/mol Al2O3
If the compound is made of ... then ... Cl- ions are needed and the formula would be ... Cu1+ and Cl1- 1 CuCl Cu2+ and Cl1- 2 CuCl2 Cu3+ and Cl1- 3 CuCl3
CuxCly (aq) + Zn (s) ---> ZnCl2 (aq) + Cu (s) (blue) (colorless)
1 mol Cu | |
Let a = mols Cu = g Cu x | ------------ |
63.55 g Cu |
1 mol Cl | |
Let b = mols Cl = g Cl x | ------------ |
35.45 g Cl |