EMPIRICAL FORMULA: Simplest whole number ratio of atoms of each Element in the Compound
s- Calculated from knowledge of the ratio of masses of each Element in the Compound
Example:
s
A compound that contains 10 g of Hydrogen and 80 g of Oxygen has an empirical formula of H2O. This can be shown by the following calculations:
s
Amount of Hydrogen Atoms = Mass in Grams ÷ Ar of Hydrogen = (10 ÷ 1) = 10 Mol
Amount of Oxygen Atoms = Mass in Grams ÷ Ar of Oxygen = (80 ÷ 16) = 5 Mol
The Ratio of Moles of Hydrogen Atoms to Moles of Oxygen Atoms:
Hydrogen Oxygen
Moles 10 : 5
Ratio 2 : 1
Ratio of Hydrogen Atoms to Oxygen Atoms is 2: 1
Hence, the Empirical Formula is H2O
|
MOLECULAR FORMULA: Exact number of atoms of each Element present in the formula of the Compound
s- Divide the Relative Formula Mass of the Molecular Formula by the Relative Formula Mass of the Empirical Formula
- Multiply this to each number of Elements
RELATIONSHIP BETWEEN EMPIRICAL AND MOLECULAR FORMULA:
s
NAME OF COMPOUND
|
EMPIRICAL FORMULA
|
MOLECULAR FORMULA
|
METHANE
|
CH4
|
CH4
|
ETHANE
|
CH3
|
C2H6
|
ETHENE
|
CH2
|
C2H4
|
BENZENE
|
CH1
|
C6H6
|
Example:
s
The Empirical Formula of X is C4H10S1 and the Relative Formula Mass of X is 180
s
What is the Molecular Formula of X?
s
RELATIVE FORMULA MASS: Carbon : 12 Hydrogen : 1 Sulfur : 32
STEP 1 - Calculate Relative Formula Mass of Empirical Formula
( C x 4 ) + ( H x 10 ) + ( S x 1) = ( 12 x 4 ) + ( 1 x 10 ) + ( 32 x 1) = 90
STEP 2 - Divide Relative Formula Mass of X by Relative Formula Mass of Empirical
Formula
180 / 90 = 2
STEP 3 - Multiply Each Number of Elements by 2
( C 4 x 2 ) + ( H 10 x 2 ) + ( S 1 x 2 ) = ( C 8 ) + ( H 20 ) + ( S 2 )
Molecular Formula of X = C8H20S2
|
No comments:
Post a Comment