# Ch1-3lsn6_105 - Chemistry at Winthrop University

```Topics
Physical vs chemical
 Extensive vs Intensive
 Units of measure
 Dimensional analysis and significant
figures

Chapters 1-3 Lesson 6
Problems 2.115 & 2.116
Classify each of the following as a
compound, a homogeneous mixture, or a
heterogeneous mixture
Distilled water
orange juice
Gasoline
vegetable soup
Beach sand
cement
Wine
calcium sulfate
Air
tea

Chapters 1-3 Lesson 6
Problems 2.115 & 2.116
homogeneous mixture
Gasoline
Wine
Air
Tea
 heterogeneous mixture
Beach sand orange juice
cement
vegetable soup
 compound
Distilled water
calcium sulfate

Chapters 1-3 Lesson 6
1-80

Carry out the following calculation, and
report the answer with the correct number
of significant figures.

(1.68) 23.56 – 2.3
1.248 X 103
Chapters 1-3 Lesson 6
Chemical Problem Solving: A Systematic
Approach to Solving Chemistry Problems
What is the price of 325 cm of wire if the
wire costs \$0.15/ft?
2.54 cm = 1.0 in
12.0 in = 1.0 ft
Chapters 1-3 Lesson 6
Chemical Problem Solving: A Systematic
Approach to Solving Chemistry Problems
Price of 325 cm of wire @ \$0.15/ft?
 2.54 cm = 1.0 in & 12.0 in = 1.0 ft
 325
cm 1.0 in 1.0 ft \$0.15
-------- ------ ------ = \$1.60
2.54 cm 12.0 in 1.0 ft
Chapters 1-3 Lesson 6
Measurement in Scientific Study: Some
Important SI Units in Chemistry
 PROBLEM
1.3
If you submerge a steel cube 15.0
mm on each side in 31.8 mL of water
in a graduated cylinder, what is the
total volume (in L) of the cylinder
contents?
31.8 mL
Chapters 1-3 Lesson 6
Measurement in Scientific Study: Some
Important SI Units in Chemistry
 PROBLEM
1.4
If a raindrop weighs 65 mg on
average and 5.1 x 105 raindrops fall
on a lawn every minute, what mass
(in kg) of rain falls in 1.5 h?
Chapters 1-3 Lesson 6
Measurement in Scientific Study: Some
Important SI Units in Chemistry
 PROBLEM
1.5
The piece of galena in Sample
Problem 1.3 has a volume of 4.6 cm3.
If the density of galena is 7.5 g/cm3,
what is the mass (in kg) of that piece
of galena?
Chapters 1-3 Lesson 6
Uncertainty in Measurement: Significant Figures:
Determining Which Digits Are Significant

PROBLEM 1.7
For each of the following quantities,
underline the zeros that are significant
figures and determine the number of
significant figures (sf) in each quantity. For
(d) to (f), express each in exponential
notation first.
– (a) 31.070 mg
– (b) 0.06060 g
– (c) 850. oC
(d) 200.0 mL
(e) 0.0000039 m
(f) 0.000401 L
Chapters 1-3 Lesson 6
Problem 2.18

Fluorite, a mineral of calcium, is a
compound of the metal with fluorine.
Analysis shows that a 2.76-g sample of
fluorite contains 1.42-g of calcium.
Calculate the (a) mass of fluorine in the
sample; (b) mass fractions of calcium and
fluorine in fluorite; (c) mass percents of
calcium and fluorine in fluorite.
Chapters 1-3 Lesson 6
MTS 2

Write the notation for
each atomic depiction.
47 e-
28 e47 p+
62 n0
28 p+
33 n0
Chapters 1-3 Lesson 6
MTS 3
Calculating an atomic mass from isotopic
composition (SP2.3)
 Magnesium has three naturally occurring
isotopes, 24Mg (isotopic mass 23.9850
amu, abundance 78.99%), 25 Mg (isotopic
mass 24.9858 amu, abundance 10.00%),
and 26Mg (isotopic mass 25.9826 amu,
abundance 11.01%). Calculate the atomic
mass of magnesium. (EOT 2.46)

Chapters 1-3 Lesson 6
MTS 3
 Calculating
an atomic mass from
isotopic composition (SP2.3)
 Copper has two naturally occurring
isotopes, 63Cu (isotopic mass 62.9396
amu) and 65Cu (isotopic mass
64.9278 amu). If copper as an
atomic mass of 63.546 amu, what is
the percent abundance of each
isotope? (EOT 2.48)
Chapters 1-3 Lesson 6
Problem 4
A flask has a mass of 78.23 g when empty and 593.63 g when
filled with water. When the same flask is filled with
concentrated sulfuric acid, H2SO4, its mass is 1026.57 g.
What is the density of concentrated sulfuric acid? The density
of water at 25 oC is 0.99707 g/cm3.
Mass H2O = 593.63 g – 78.23 g = 515.40 g
Volume H2O = m/D = 516.9146 cm3
Mass H2SO4 = 1026.57 g – 78.23 g = 948.34 g
D H2SO4 = m/V = 1.834616 g/cm3 = 1.8346 g/cm3
Chapters 1-3 Lesson 6
Problem 6
Hoffmannium has three common isotopes: 336Hm,
338Hm, and 340Hm. If the abundance of 340Hm
is 5.023 %, what are the abundances of 336Hm
and 338Hm? The mass of 336Hm is 335.99452
amu, 338Hm is 337.98638 amu, and 340Hm is
339.97481 amu. The mass of naturally occurring
hoffmannium is 336.8751 amu.
60.8% =
336Hm
34.2% =
Chapters 1-3 Lesson 6
338Hm
Problem 3
The average density of the Earth is
5.52 g/cm3. What is the density in
lb/ft3?
345 lb/ft3
Chapters 1-3 Lesson 6
Chemical Problem Solving: A Systematic
Approach to Solving Chemistry Problems
A
furniture factory needs 31.5 ft2 of
fabric to upholster one chair. Its Dutch
supplier sends the fabric in bolts of
exactly 200 m2. What is the maximum
number of chairs that can be
upholstered by 3 bolts of fabric (1 m =
3.281 ft)?
Chapters 1-3 Lesson 6
Measurement in Scientific Study: Some
Important SI Units in Chemistry
 PROBLEM
1.6
Mercury melts at 234 K, lower than
any other pure metal. What is its
melting point in oC and oF?
T (K) = T (oC) + 273.15
T (oC) = T (K) – 273.15
T (oF) = 9/5 T (oC) + 32
= 1.8 T (oC) + 32
Chapters 1-3 Lesson 6
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