AP Chemistry – Answers to Questions Chapter 1
2) a.
636.3g 1 penny = 210 pennies
3.03 g
Sig. Figs. = 2.10 x 102 pennies
c.
210 pennies 2 dimes 2.29 g = 320.6 g
3 pennies 1 dime
Sig. Figs. = 321 g
e.
210 pennies 1 candy bunch
4 pieces
10.23 g = 2864.4 g
3 pennies
1 candy bunch 1 piece
Sig. Figs. = 2864 g
4) iii – mass cannot be created or destroyed
8) When reading values on laboratory instruments the value included should be all that
are seen with the markings on the instrument and one estimate. When reading volumes
of liquids, the meniscus is the position from which the reading should be taken. The
graduate with the yellow solution has markings to the two tenths, not every single tenth,
making the tenth place the estimated position. The meniscus is found between the lines
representing 2.8 and 3.0. It is less than halfway to the 3.0. A value of 2.8 or 2.9mL
would be appropriate. For the graduate with the green solution the markings go to the
two hundredths place therefore the reading should be to the hundredths. The meniscus
appears to be on the line representing 0.28mL making that the correct reading. The last
things that must be considered are the rules for adding and subtracting with significant
digits. The answer can only be placed as far to the right as the LEAST far to the right
number in the problem. 2.8mL + 0.28mL = 3.08 which needs to be rounded to 3.1mL as
the answer can only go to the tenth place. 2.9mL + 0.28mL = 3.18 which would round to
3.2mL. 3.1mL or 3.2mL would be the correct answer. The precision of the sum is
dependent on the less precise instrument, the one with tenths rather than hundredths
markings.
13) One cylinder should have markings to the hundredths place so that it can be read to
the thousandths, the other should have markings to the tens to be read to the ones.
20) The scientific method is considered a dynamic process because it is active not static.
Scientists do not quit asking questions just because a known theory SEEMS to account
for a behavior. They continue to experiment in different ways to verify, nullify, or
modify current theories and/or hypothesis.
24) a. 9.4cm, 9.8cm, and 9.6cm would be an inaccurate and imprecise set of data. They
are all off about 1cm and they are made to the tenths rather than the hundredths.
c. 10.62cm, 10.63cm, and 10.61cm would be accurate and precise. They are within
0.02cm of each other (normal acceptance is a variance of 2 in the estimated value
position). They are precise because they are measured to the hundredths as allowed by
the instrument according to the problem.
28) a. homogeneous mixture – air, brass, kool-aid, and tea – the SAME throughout and
in close physical proximity.
c. compound – salt, sugar, water, and carbon dioxide – chemically combined with
bonds.
e. physical change – boiling, sublimation, tearing paper, coloring – does not change
any of the chemical bonds, only physical characteristics.
32)
a. 1
c. 4
e. 2
g. 3
36) a. The answer comes out to 2.263521386. As all of the values in the set up have 3
significant digits, and multiplication and division are the processes involved, the answer
should be rounded to 2.26.
c. These values have 2, 4, and 6 significant digits respectively. As the process being
used is multiplication, the answer can only be as significant as the least significant value
in the set up, meaning that it may have only 2 significant digits. The answer of 1.476x105
is therefore rounded to 1.5x105.
40) a.
1 Tg 1x1012 g 1 kg = 1x109 kg
1 Tg
1000 g
c.
25 fg
e.
1mL
1g
1 kg = 2.5x10-17 kg
15
1x10 fg 1000 g
1L
1x106 µL = 1x103 µL
1000 mL
1L
42) a.
908 oz
c.
125 mL
1 lb 0.4536 kg = 25.7 kg
16 oz
1 lb
1L
1 qt
= 0.132 qt
1000 mL 0.9463 L
e.
4.48 lb 453.6 g = 2.03x103 g
1 lb
This answer needs to be in scientific notation to show the proper number of significant
digits.
48)
100. m
9.74 s
= 10.3 m/s
100. m
9.74 s
60 s
1 min
100. m
9.74 s
1.0936 yd
1m
3 ft
1 yd
= 33.7 ft/s
100. m
9.74 s
1.0936 yd
1m
3ft
1 yd
1 mi
5280 ft
60 min
1 hr
56) a. TC = TK – 273.
TF = 1.8(TC) + 32.
c.
1 km
1000 m
= 37.0 km/hr
60 s
1 min
60 min = 23.0 mi/hr
1 hr
233 – 273 = -40.oC
1.8(-40.) + 32 = -40 oF
298 – 273 = 25oC
1.8(25) + 32 = 77oF
60) D = m/V.
Volume – 4/3 x 3.14 x (0.50cm)3 = 0.52cm3
Density = 2.0g/0.52cm3 = 3.8g/cm3
The density of the sphere is greater than the density of water and it will sink.
66) V = m/D.
V = 5.25g/10.5g/cm3 = 0.500cm3 or 0.500mL (1cm3 = 1 mL) is the volume of the
silver. 11.2mL + 0.500mL = 11.7mL.
74) --------78) When the magnesium and sulfur are placed together there is a heterogeneous
mixture. When this mixture is heated it forms magnesium sulfide, a compound with
different characteristics than the original magnesium and sulfur, and it is no longer a
mixture because chemical bonds were formed.
82) a. This indicates a mixture because a yellow liquid has been separated from the red
solid through distillation which is a physical change.
c. This indicates a mixture because dissolving is a physical change.
88) The density of the second ingredient is 0.384g/0.32cm3 = 1.2g/cm3, which matches
with caffeine according to the table.