1. Chemical Formula’s

2. Chemical formula
Used to express the composition of molecules and ionic compounds in terms of chemical symbols

3. Empirical
Molecular
Tells us which elements are present and in the simplest whole- number ratio of their atoms
Based on observation or measurement
Shows the exact number of atoms of each element in the smallest unit of a substance
Multiple of the empirical formula

4. Practice
(1) Identify the following formulas as empirical, molecular, or both. (2) Determine the empirical formula(s) for the molecular formulas identified. NH3, C6H12O6, CH2O, B2H6, H2S

5. How to determine Molecular formulas
Calculate the molar mass of the empirical formula.
Determine the multiplier by dividing the molar mass given by the molar mass of the empirical formula (#1)
Multiply the subscripts of the empirical formula by the multiplier determined in #2

6. example
The empirical formula of a compound is C2H3O2. If the molar mass of the compound is g/mol, what’s the molecular formula?

8. Formula of a hydrate
Hydrates are compounds that have a specific number of water molecules attached to them.
Anhydrate is the substance that remains after the water is removed (ionic compound)
Example: CuSO45H2O

9. Naming hydrates CuSO4  5H2O Ionic compound Hydrate Greek prefix
Copper(II) sulfate pentahydrate