Lowest whole ratio H 2 O 2 hydrogen peroxide is it a empirical Formula No you can reduce it to HO H 2 O 2 is the molecular formula Molecular formula shows the way the molecule is actually found in nature ID: 917093
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Slide1
Empirical Formulas
Slide2Empirical Formula: Lowest whole # ratio
H
2
O
2
(hydrogen peroxide) is it a empirical Formula?
No, you can reduce it to HO
Slide3H2O
2
is the molecular formula
Molecular formula shows the way the molecule is actually found in nature.
Slide4How do we write empirical formulas???
1. Take the % compositions and convert the % to grams.
Slide511.1 % H 88.9% O changes to
11.1 g H 88.9 g O
Slide6Take the % compositions and convert the % to grams.
Convert grams to moles
Slide711.1 g H x 1 mole H
= 11.1 moles
1.0 g H
88.9 g O x
1 mole O
= 5.5 moles
16.0 g O
Slide8Take the % compositions and convert the % to grams.
Convert grams to moles
Divide by the smallest # of moles
Slide911.1 moles H / 5.5= 2
5.5 moles O / 5.5 =1
Slide10Plug the whole #’s into the empirical formula
Take the % compositions and convert the % to grams.
Convert grams to moles
Divide by the smallest # of moles
Slide1111.1 moles H / 5.5= 2
5.5 moles O / 5.5 =1
H
2
O
1
Slide12Take the % compositions and convert the % to grams.
Convert grams to moles
Divide by the smallest # of moles
Plug the whole #’s into the empirical formula
If you do not have whole #’s after dividing you must multiply through to make them all whole #’s
Slide13Examples1.5 x 2 = 3
1.3 x 3 = 4
1.25 x 4 = 5
1.75 x 4 = 7
Slide14ExamplesMn
1
O
1.5
2x (Mn
1
O
1.5
)=
Mn
2
O
3
Slide15Molecular Mass Vs.
Empirical Mass
Slide16Molecular Mass Is found experimentally
Slide17Empirical MassIs found using the molar mass from the periodic table.
Slide18Molecular Mass Vs.
Empirical Mass
If they are the same
GREAT
the Molecular Formula and Empirical Formula are the same
Slide19Molecular Mass Vs.
Empirical Mass
If they are not the same you must divide the Molecular mass by the Empirical mass to see how many time greater it is.
Slide20Molecular Mass Vs.
Empirical Mass
Molecular mass = 78g/mol
Empirical mass
of CH =13g/mol
78/13 =6
Slide21Molecular Mass Vs.
Empirical Mass
Since the molecular mass is 6 times greater then the empirical mass the formula is also 6 times greater.
Slide22Molecular Mass Vs.
Empirical Mass
6 x (CH)
C
6
H
6
Molecular Formula