Page 255 - Chemistry eBook

Finding the Molecular Formula from the Empirical Formula: Problem
If the empirical formula is CH2O and the molecular mass is 180 grams, what is the molecular formula?
Answer:
1. Mass of empirical formula:
C: 12
H: 1 x 2 = 2 (atomic mass × subscript) O: 16
12 + 2 + 16 = 30
2. Mass of the molecular formula’s mass Mass of empirical formula
180 = 6 30
3. Multiply each element by 6: CH2O × 6
C1 x 6 = 6, H2 x 6 = 12, O1 x 6 = 6 Molecular formula: C6H12O6
UNIT 6: MATH IN CHEMISTRY © 254