Percent Comp
CuSO4.5H2O
% Composition
CuSO4. 5 H2O
1 Cu = 1 (63.55 g) = 63.55 g
1 S = 1 (32.06 g) = 32.06 g
4 O = 4 (16.00 g) = 64.00 g
5 H2O = 5 (18.02 g) = 90.10 g
249.71 g
% Composition
(Continued)
% Cu = 63.55 g/249.71g (100 %) = 25.45 % Cu
% S = 32.06 g/249.71 g (100 %) = 12.84 % S
% O = 64.00 g/249.71 g (100 %) = 25.63 % O
% H2O = 90.10 g/249.71 g (100 %) = 36.08 % H2O
Check: Total percentages. Should be equal to 100 %
plus or minus 0.01 %.
Formulas
-- Empirical formula is the empirical
formula of a compound.
NaCl CaCl2
-- Molecular formula – is the actual ratio
of atoms I the compound .
C6H12O6 C2H6
The analysis of a rocket fuel
showed tht it contained 87.4%
nitrogen and 12.6 % hydrogen
by weight .
Mass spectral analysis showed
the fuel to have a molar mass of
32.05 grams .
What are the empirical and
molecular formulas of the fuel?
Empirical Formula Determination
from percent
1. Base calculation on 100 grams of
compound.
2. Determine moles of each element in 100
grams of compound.
3. Divide each value of moles by the smallest
of the values.
4. Multiply each number by an integer to
obtain all whole numbers.
Formula of a Compound Calculations
Determine the empirical and molecular
formulas for a deadly nerve gas the
gives the following percent analysis .
C=39.10 % H=7.67% O=26.11%
P=16.82% F=10.30%
Molecular Mass =552.3g
Empirical Formula Determination
1. Determine moles of each
element in the compound.
2. Divide each value of moles
by the smallest of the values.
3. Multiply each number by an
integer to obtain all whole
numbers.
Study guide P.68- 71
Q: 3,10,45-47
Calculating Empirical Formulas
Determine the empirical formula of
a compound that contains
4.151 g Al & 3.692 g O
Practice
Determine the empirical formula and
molecular formula of the following
gas.
molar mass=184.1g
C=39.1% H=7.67% O=26.11%
P=16.82% F=10.30%
Combustion empirical
Combustion data
A combustion device was used to
determine the empirical formula of a
compound containing only carbon
,hydrogen, and oxygen. A 0.6349g
sample of the unknown produced
1.603g of CO2 and .2810g H2O.
Determine the empirical formula of the
compound.
A combustion device was used to determine
the empirical formula of a compound
containing only carbon, hydrogen, and
oxygen. A .6349 g sample of the unknown
produced 1.603 g of CO2 and .2810 g of
H2O. Determine the empirical formula of
the compound.