Chemistry Reference
In-Depth Information
2.175
Volume of water
volume of alcohol
V
mL
85.63 g C
100.0 g total
3.14 (a)
(b)
There is 7.78 g of carbon in any 9.08-g portion because of
the law of definite proportions.
9.08 g total
a
b
7.78 g C
Mass of water
1.00
V
g
Mass of alcohol
0.789
V
g
Total mass
1.79
V
g
Density
m
V
3.15
3.18
Protons and electrons
3.19 (a)
V
(b)
Na
(c)
V is in group VB; Na is in group IA.
3.20 (a)
38.0 g
(b)
4.73 g
12.11 g
16.84 g
1 mL
0.942 g
V
solution
m
d
(1.79
V
g)
a
b
1.90
V
mL
The volume of the solution is 1.90 times that of the water
(and of the alcohol).
1 mL acid
1.8305 g acid
8(30.0 g)
12(46.0 g)
20
2.178
99.00 g acid
a
b
54.08
4
mL acid
39.6 g
1.000 mL water
54.08
4
mL acid
55.08
4
mL total
3(35.0 amu)
37.0 amu
(c)
35.5 amu
1 mL solution
1.8342 g solution
4
100.00 g solution
a
b
3.21
Atomic numbers had not been developed at the time
Mendeleyev did his work. Atoms were still thought to be in-
divisible.
3.22
Elements with atomic numbers 61, 84-87, 89, and 94 and higher
have mass numbers given because they do not occur naturally.
3.23
The total mass of the reactants must equal the total mass of the
products:
54.519
7
mL solution
The change in volume is
55.08
4
mL total
54.519
7
mL solution
0.56 mL
2.179
There is 1.00 g water and
a
1.8305 g acid
1 mL acid
b
98.99
3
g acid
54.08 mL acid
31.9 mg
x
87.7 mg
71.8 mg
The total mass is 99.99
3
g, and the density is
x
127.6 mg oxygen
99.99
3
g
54.52 mL
1.834 g/mL
3.25 (a)
7.33 g
7.05 g
0.28 g oxygen
0.28 g
7.33 g
0.038
(b)
(c)
3.8%
10
2
m
3
a
10
3
L
1 m
3
1
L
10
6
L
10
7
2.183
2.55
b
a
b
2.55
L
a
3.454 g Cl
2.241 g Na
3.27 (a)
(b)
0.4675 g Na
3.29 (a)
For each atom of A present, the mass of B present is
amu, and the mass of A present is 24.3 amu.
The ratio is therefore
(254 amu B)
15.44 g Na
b
23.80 g Cl
3 Atoms and Atomic Masses
5
2
2.50
1
3.1
2
127
254
The gambler wins $2.50 for each dollar bet. Although 2.50
1
is not an integral ratio, it is equal to the integral ratio 5
2.
(24.3 amu A)
(b)
The ratio of atoms (2 : 1) is integral.
3.30
No; the law of multiple proportions involves two compounds
containing the same elements (such as SO
2
and SO
3
), in
which the ratio of masses of one element is a small, whole-
number ratio (for a given mass of the other element).
3.34 (a)
Per gram of element 2 (E2):
First compound
(10.5 units B)
(unit A)
3.2
(b)
3.05 g (exactly half of 6.10 g)
(c)
12.2 g (exactly double 6.10 g)
Note that
(a)
is the
same
compound.
12
C
3.3
The mass of
3.4
Chemists use atomic mass and atomic weight as synonyms.
All the other terms have different meanings.
3.5
(a)
19
(b)
19
(c)
19
The three parts actually ask the same question in different words.
Second compound
92.26 g E1
7.74 g E2
11.92 g E1
1 g E2
85.63 g E1
14.37
g E2
5.959 g E1
1 g E2
3.6
Atomic number:
(a)
65
Atomic mass:
(b)
101.07
(the only noninteger)
Per gram of E2, the ratio of E1 is
Mass number:
(c)
(242)
(too high for an atomic num-
ber, and in parentheses)
11.92 g
5.959 g
2 g
1 g
3.7
(a)
e,
the charge on the electron
(b)
amu
(b)
This is exactly the same problem with the data presented
in a different order.
Be sure to calculate per gram of one
of the elements.
3.36 (a)
1.234 g or
(b)
4.936 g.
Either is a small whole-number ratio, as required by the
law of multiple proportions.
[
(d)
is the same compound.]
3.37 (a)
It is amended or discarded entirely.
7(5.55 g)
2(6.42 g)
3(4.21 g)
3.8
5.36 g
3
7
2
3.9
Mass
3.10
The symbol for the isotope has a superscript on its left side,
denoting the mass number.
3.11
Atomic number and atomic mass
3.12
The mass number is an integer—the number of protons plus
neutrons. The mass is an actual measured quantity and is not
integral.
3.13 (a)
84.9 g
(b)
13.0 g
(c)
23.7 g
(d)
The law of conservation of mass for part (a), and the law
of definite proportions for parts (b) and (c)
(b)
The fifth
65.4 amu
32.1 amu
2.04
3.39 (a)
(b)
6540 amu Zn; 3210 amu S
(c)
6540 amu
3210 amu
2.04
