Chemistry Reference
In-Depth Information
6.
[3.01 moles]—
# of molecules
Avogadro's number
1.81 × 10
24
molecules
6.02 × 10
23
molecules/mole
# of moles =
=
= 3.01 moles
7.
[1.51 × 10
24
molecules]
a. First, find the molar mass of water: 2.02 g + 16.0 g = 18.0 g/mole
mass
molar mass
45.0 g
18.0 g/mole
= 2.50 moles
b.
# of moles of water =
=
c.
# of molecules = # of moles × Avogadro's number
= 2.50 moles ×
6.02 × 10
23
molecules
mole
= 1.51 × 10
24
molecules
8.
[94.3 dm
3
]—The molar mass of neon, from the periodic table, is 20.2 g/mole.
mass of sample
molar mass
85.0 g
20.2 g/mole
= 4.21 moles
a.
# of moles =
=
Volume = 4.21 moles ×
22.4 dm
3
mole
b.
= 94.3 dm
3
9.
[1.81 × 10
24
molecules]—
volume
molar volume
67.5 dm
3
22.4 dm
3
/mole
= 3.01 moles
a.
# of moles =
=
6.02 × 10
23
molecules
mole
b.
# of molecules = 3.01 moles ×
= 1.81 × 10
24
molecules
10. [2880 g]—The molar mass of water is 18.0 g/mole.
9.65 × 10
25
molecules
6.02 × 10
23
molecules/mole
= 160 moles
a.
# of moles =
18.0 g
mole
b.
Mass = # of moles × molar mass = 160 moles ×
= 2880 g
Lesson 7-3 Review
1.
[2 moles]—The ratio of propane to oxygen is
1:5. It would take 1 mole of propane to react
completely with 5 moles of oxygen, and 2 moles
of propane to react with 10 moles of oxygen.
The adjacent ratio may help.
propane oxygen
coefficients
moles
1
x
5
10
=
5x = 10, x = 2
propane oxygen
2.
[15 moles]—
coefficients
1
3
5
x
=
moles
x = 15
3.
[12 moles]—
propane water
coefficients
1
3
4
x
=
moles
x = 12
4.
[10 moles]—
propane carbon dioxide
coefficients
1
x
3
30
=
moles
3x = 30, x = 10
