HOMEWORK # 1 KEY
Chapter 1
5. An incandescent light bulb converts electrical energy into light energy. Yet it also
releases a significant amount of energy as heat. The law of conservation of energy is
observed, since the sum of heat and light energy produced is equal to the electrical
energy consumed.
9. (a) a soft drink is a mixture (water + dissolved components, carbonic acid, CO2 gas).
(b) water is a compound, H2 O
(c) air is a mixture of gases (and often particulate pollution)
(d) chicken noodle soup is a heterogeneous mixture of broth, noodles, grease, etc.
(e) pure table salt is a compound, sodium chloride (NaCl). However, many
commercially available samples of table salt are a mixture of sodium chloride
with other materials.
(f) popcorn is a mixture of popped & unpopped kernels, oil, salt. But even if you
pick out all the unpopped kernels and eat it oil & salt free, looking at the nutrition
information reveals that popcorn is a mixture of many things, including fiber and
carbohydrates.
(g) Aluminum foil is an element (aluminum).
25. (a) not exact (probably measured)
(b) exact (counted)
(c) exact (counted to the nearest penny)
(d) not exact (obtained by measurement)
(e) not exact (obtained by measurement)
(f) exact (although of questionable accuracy, counted)
35. 16 gallons x
41. (a) mass of H2 O
volume of H2 O
4 quarts x
1 Liter
1 gallon
1.057 quarts
x
$0.325 =
1 Liter
2 sig figs
=
$19.67
$20
= 91.44 g – 73.91 g = 17.53 g H2 O
= 17.53 g H2 O x
1 cm3
1.0000 g
=
(b) mass of unknown liquid = 88.42 g - 73.91 g = 14.51 g
density of unknown liquid = 14.51 g
17.53 cm3
=
0.8277 g/ cm3
17.53 cm3
Chapter 2
13. (a)
(b)
(c)
(d)
(e)
magnesium chloride
copper (II) nitrate
lithium sulfate
calcium hydroxide
iron (II) sulfate
15. (a)
(b)
(c)
(d)
(e)
Na2 S
Al2 (SO4 )3
Na3 PO4
Mg(NO3 )2
Fe2 (CO3 )3
27. (a)
Ca
S
O4
1(40.078) =
1(32.066) =
4(15.9994) =
40.078
32.066
63.9976
136.142 amu
(b)
C4
H10
4(12.011) =
10(1.0079) =
48.044
10.0790
58.123 amu
(c)
C6
H8
S
O2
N2
6(12.011) =
8(1.0079) =
1(32.066) =
2(15.9994) =
2(14.0067) =
72.066
8.0632
32.066
31.9988
28.0134
172.207 amu
(d)
3U
14O
2P
29.
3(238.0289) =
14(15.9994) =
2(30.9738) =
8.575 g Ne
20.1797 g Ne per mole
=
714.0867
223.9916
61.9476
1000.0259 amu
0.4249 mole Ne
39. (a)
1.24 mol C6 H12 O6 x 6.022 x 1023 molecules = 7.47 x 1023 C6 H12 O6 molecules
1mol C6 H12 O6
7.47 x 1023 C6 H12 O6 molecules x
6 C atoms
=
1 C6 H12 O6 molecule
4.48 x 1024 C atoms
7.47 x 1023 C6 H12 O6 molecules x
12 H atoms
=
1 C6 H12 O6 molecule
8.96 x 1024 H atoms
7.47 x 1023 C6 H12 O6 molecules x
6 O atoms
=
1 C6 H12 O6 molecule
4.48 x 1024 O atoms
3.31 x 1019 C6 H12 O6 molecules x
6 C atoms
=
1 C6 H12 O6 molecule
1.99 x 1020 C atoms
3.31 x 1019 C6 H12 O6 molecules x
12 H atoms
=
1 C6 H12 O6 molecule
3.97 x 1020 H atoms
3.31 x 1019 C6 H12 O6 molecules x
6 O atoms
=
1 C6 H12 O6 molecule
1.99 x 1020 O atoms
(b)
(c)
0.275 g C6 H12 O6
x 1 mol C6 H12 O6
180.16 g
x
6.022 x 1023 molecules
1mol C6 H12 O6
= 9.19 x 1020 C6 H12 O6 molecules
9.19 x 1020 C6 H12 O6 molecules x
6 C atoms
=
1 C6 H12 O6 molecule
5.51 x 1021 C atoms
9.19 x 1020 C6 H12 O6 molecules x
12 H atoms
=
1 C6 H12 O6 molecule
1.10 x 1022 H atoms
9.19 x 1020 C6 H12 O6 molecules x
6 O atoms
=
1 C6 H12 O6 molecule
5.51 x 1021 O atoms
Chapter 3