Chemistry Reference
In-Depth Information
EXAMPLE 7.9
Calculate the number of moles of hydrogen atoms in 6.170 mol of
H
2
O.
Solution
2 mol H
1 mol H
2
O
6.170 mol H
2
O
a
b
12.34 mol H
Moles of
H
2
O
Chemical
formula
Moles of
H atoms
Factor from
chemical formula
Practice Problem 7.9
Calculate the number of moles of aspirin,
10
23
C
9
H
8
O
4
,
that contains
4.21
oxygen atoms.
EXAMPLE 7.10
(a) Calculate the number of grams of fluorine in 7.197 g of
(b) Calculate the mass of
CaF
2
.
CaF
2
that contains 7.197 g of fluorine.
Solution
(a) The molar mass (atomic mass in grams per mole) of fluorine is 19.00 g/mol;
the molar mass of
CaF
2
is 78.08 g/mol.
Mass
of CaF
2
Molar
mass
Moles
of CaF
2
Chemical
formula
Moles of
F atoms
Atomic
mass
Mass
of F
Therefore,
(
)
(
)
(
)
3.503 g F
1 mol CaF
2
78.08 g CaF
2
2 mol F
1 mol CaF
2
19.00 g F
1 mol F
7.197 g CaF
2
(b)
Mass
of F
Atomic
mass
Moles
of F
Chemical
formula
Moles
of CaF
2
Molar
mass
Mass
of CaF
2
(
)
(
)
(
)
14.79 g CaF
2
1 mol F
19.00 g F
1 mol CaF
2
78.08 g CaF
2
7.197 g F
2 mol F
1 mol CaF
2
Practice Problem 7.10
(a) Calculate the mass of phosphorus in 1.50 kg of
(NH
4
)
3
PO
4
,
a principal
constituent of many fertilizers.
(b) Calculate the mass of
(NH
4
)
3
PO
4
that contains 1.50 kg of phosphorus.
