unit v: the mole concept v.5. empirical and molecular formulae
TRANSCRIPT
Unit V: The Mole Concept
V.5. Empirical and Molecular Formulae
Empirical Formula
Empirical Formula Simplest Formula Gives the simplest whole number ratio of
elements in a compound
Molecular Formula
Molecular Formula Gives the ACTUAL number of each kind of atom
in a molecule and compound
Molecular vs. Empirical
Molecular vs. Empirical
Molecular Formula Empirical Formula
P4O10
C10H22
C6H18O3
C5H12O
N2O4
Molecular vs. Empirical
Molecular Formula Empirical Formula
P4O10 P2O5
C10H22 C5H11
C6H18O3 C2H6O
C5H12O C5H12O
N2O4 NO2
Finding Empirical Formulas
A sample of an unknown compound is analyzed and found to contain 8.4 g of “C” 2.1 g of “H” and 5.6 g of “O”.
Find the empirical formula.
Finding Empirical Formulas
Element Mass (g)
AtomicMass
Moles MolesSm.Moles
SmallestRatio
C
H
O
Finding Empirical Formulas
0.888 grams of a compound made up of carbon, hydrogen and oxygen are found to contain 0.576 g of carbon and 0.120 g of hydrogen.
a) Find the mass of oxygen
b) Find the empirical formula
Finding Empirical Formulas
Element Mass (g)
AtomicMass
Moles MolesSm.Moles
SmallestRatio
C
H
O
Finding Empirical Formulas
A while powder used in paints has the following composition:
Ba 69.58% C 6.090% O 24.32%
Find the Empirical Formula
Finding Empirical Formulas
Element Mass(g) AtomicMass
Moles MolesSm.Moles
SmallestRatio
Ba
C
O
WHAT HAPPENS WHEN…….. is not near a whole # __ Moles__
smallest moles
If ends in
a decimal of
Multiply ALL numbers by…. to get the Smallest
Ratio
≈ 0.5 2
≈0.33 or ≈0.66 3
≈0.25 or ≈0.75 4
≈0.2, ≈0.4, ≈0.6, ≈0.8 5
molessmallest
moles
Empirical to Molecular Formula A compound has a molar mass of 60.0g/mol and its
empirical formula is CH2O. Find the molecular formula.
Empirical Molecular
Formula
Mass
Hebden
Do Exercises 46 (d, g, & m) on pages 93 & Exercises 48 and 52 on page 95 of Hebden
Read through Tutorial 5-1: Percent Mass and Empirical Formulas (Working in Pairs)
Do the Self-Test on Tutorial 5-1