c. johannesson ch. 4 - molar relationships iii. percent composition (p. 143-144)
DESCRIPTION
C. Johannesson 100 = B. Calculation of % Comp n Find the % composition of FeO. %Fe = g g 100 = %O = g g 77.73% Fe 22.27% OTRANSCRIPT
C. Johannesson
Ch. 4 - Molar Relationships
III. Percent Composition(p. 143-144)
C. Johannesson
A. Definition the percent by mass of each element
in a compound
100mass totalelement of massncompositio %
to distinguish between similar compounds to determine elemental mass in a sample
C. Johannesson
100 =
B. Calculation of % Comp Find the % composition of FeO.
%Fe =55.85 g71.85 g
100 =
%O =16.00 g71.85 g
77.73% Fe
22.27% O
C. Johannesson
100 =
B. Calculation of % Comp Find the % composition of Fe2O3.
%Fe =111.70 g159.70 g
100=
%O =48.00 g
159.70 g
69.944% Fe
30.06% O
C. Johannesson
C. Compound Identification A compound contains 28 g Fe and 8.0 g O. Is it
FeO or Fe2O3?
%Fe =28 g36 g
100 =
The compound is FeO.
78% Fe
C. Johannesson
D. Elemental Mass in a Sample How many grams of iron are in a
38.0-gram sample of iron(III) oxide?
38.0 g Fe2O3 69.944 g Fe100 g Fe2O3
= 26.6 g Fe
Fe2O3 is 69.944% Fe
- or -
(38.0 g Fe2O3)(0.69944) = 26.6 g Fe
C. Johannesson
CHALLENGE PROBLEM A mining company needs to choose a mine site.
Which would provide a better source of iron? Ore containing 32% FeO or ore containing 48% Fe2O3?
FeO is 77.73% FeFe2O3 is 69.944% Fe
SOLUTION
C. Johannesson
100 =
E. % Water in a Hydrate
CaCl2·2H2O calcium chloride dihydrate
%H2O =36.04 g
147.02 g 24.51%
H2O
100mass total waterof massOH % 2