Chemistry Reference
In-Depth Information
6. [B. 500.]—In this case, the decimal point wouldn't be there, unless it was to
indicate that the zeros represent significant digits. This answer shows one of
the three acceptable methods for showing extra significant digits.
7. [C. 3204 g]—Answer A only shows 1 significant digit, as all of the zeros are
placeholders. Answers B and D show two significant digits.
8. [B. 2]—The measurement from the problem with the least number of
significant digits, 4.0 m, shows two significant digits. We would need to
round our answer to 2 significant digits.
9. [B. 39.1 cm]—The answer before rounding was 39.12 cm. Two of the
measurements in the problem are considered accurate to the tenth place, so
we must round the answer to the tenth place.
10. [A. 14 cm
2
]—The original answer was 13.775 cm
2
. We must round to two
significant digits because the measurement 5.0 cm shows only 2 significant
digits.
Lesson 2-5 Review
1.
1000 m
1 km
100 cm
1 m
[453000 cm]—
4.53 km ×
×
= 453000 cm
2.
[202176 s, which rounds to 202000 s]—
2.34 dy ×
24 h
1 dy
60 min
1 h
60 s
1 min
×
×
= 202176 s
3 ft
1 yd
12 in
1 ft
3.
[8.28 inches, which rounds to 8.3 inches]—
0.23 yd ×
×
= 8.28 in
4.
[1634.4 m/h, which rounds to 1630 m/h]—
45.4 cm
s
60 s
1 min
60 min
1 h
1 m
100 cm
×
×
×
= 1634.4 m/h
5.
[18.144 L/wk, which rounds to 20 L/wk]—
0.03 ml
s
3600 s
1 h
24 h
1 dy
7 dy
1 wk
1 L
1000 ml
×
×
×
×
= 18.144 L/wk
1 m
100 cm
6.
[B.
]—Remember: In order to construct a good conversion factor, the
values in the denominator and numerator must be the same. 1
m = 100 cm, but 3 yd
≠
1 ft.
1000 cm
3
1 L
7.
[D.
]—Remember: 1000 km
≠
1 m, but 1km = 1000 m!
1 g
100 cm
3
8.
[A.
]—Conversion factors must be reducible to 1.
1000 m
1 km
9.
[D.
]
1000 ml
1 L
10. [D.
]—Answers B, C, and D are all proper conversion factors, but
only the conversion factor from answer D will help us get
where we want to go.
