Chemistry Reference
In-Depth Information
B. [4]—The three is significant because it is a nonzero digit. All three zeros
are significant because they are found to the right of both a significant digit
and a decimal.
C. [1]—Only the 4 is significant, being a nonzero digit. All of the zeros are
placeholders. Some of them are to the right of a decimal, but in order to be
significant, they need to be to the right of a significant digit as well.
D. [4]—Remember, we only focus on the coefficient. The 4 and 5 are nonzero
digits, and both zeros are to the right of a decimal and a significant digit.
13. A. [57]—(53 + 3.59 = 56.59) We need to round to the “ones” place,
according to the rule for addition and subtraction.
B. [41.4]—(76.32 - 34.9 = 41.42) We need to round to the “tenth” place,
because 34.9 is considered accurate to the tenth place.
C. [
]—(3.45 x 2.9 = 10.005) We want our answer to show two significant
digits, so I put a line over the zero to make it significant. I could have used
scientific notation instead, and written 1.0 x 10
1
.
10
4.5 × 10
8
3.42 × 10
5
= 1.315789474 × 10
3
D. [1.3 x 10
3
]—( ) According to the rule for
multiplying and dividing, we want our answer to show only two significant digits.
14. [3.86 g]—
m = D × v = 0.852 g/cm
3
× 4.53 cm
3
= 3.85956 g
m
D
0.434 g
1.23 g/cm
3
15. [0.353 cm
3
]—
v =
=
= 0.3528455285 g/cm
3
16. [B. pico, nano, milli, centi]—As shown in Figure 2-1d, answer B has the
prefixes arranged from smallest to largest.
17. [C. Newton]—Although used very often in physics, the Newton is an SI-
derived unit, rather than a base unit.
18. [D. 22.9 L]—By converting all of the units to liters, we can see that none of
the other answers are nearly as large as answer choice D.
19. [Mass is a measure of the amount of matter in an object. Density is a
measure of how much matter is in a given unit of volume.]—The density of
an object is directly proportional to its mass, and inversely proportional to
its volume. The formula for density is . The density of an
object might be expressed in g/cm
3
, Kg/L, or any other unit of mass over a
unit of volume.
20. [Mass is a measure of how much matter an object has, whereas weight is a
measure of the force of attraction between two objects (one of these is
usually the Earth).]—More massive objects do weigh more than less
massive objects, under the same conditions, but there is more to weight
than just mass. The weight of an object also has to do with the distance
between it and the object (usually the Earth) that is attracting it.
mass
volume
Density =
