|
Determination
of Empirical and Molecular Formulas
Substance contains
40.0% carbon, 6.7% hydrogen, (assume remainder, 53.3% is oxygen).
Since the composition
is independent of the size of the sample, choose a 100 gram sample for
convenience.
|
Element
|
Amount
(grams)
|
Atomic
Mass (grams/mole)
|
Amount
(moles)
|
Mole
Ratio
|
Atom
Ratio
|
|
|
|
|
|
|
|
|
Carbon
|
40.0
|
12.01
|
3.33
|
1
|
1
|
|
Hydrogen
|
6.7
|
1.008
|
6.65
|
2
|
2
|
|
Oxygen
|
53.3
|
16.00
|
3.33
|
1
|
1
|
Atom ratio reexpressed:
C1H2O1, or CH2O
Molecular
Formula, M.F. (atom number); from E.F. + molecular weight:
If the
molecular weight is 30, the molecular formula is CH2O
If the
molecular weight is 60, the molecular formula is C2H4O2
If the
molecular weight is 90, the molecular formula is C3H6O3
etc.
Structural
Formula (atom connections); from M.F. + properties
|
