Download Mole Concept and Mole Conversions

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Homework ___________
Exam Date:
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Textbook
Chapter 10: pages 304-343
JHS chemistry Department ~ Mole Concept & Mole Conversions 15-16
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Mole Concept and Mole Conversions Student Outline
Mole: a unit used by chemists to express the amount of a compound or element
Avogadro’s Number = 6.02 x 1023 molecules (The number of molecules in 1 mole of a substance)
Molar volume of gas: 22.4 L at STP
Molar mass of a substance (molecular mass, gram formula mass~ GFM): mass of all atoms in the formula expressed
in grams. Be careful with the diatomics!
Mole conversion methods:
 Factor-label


ratio method
The Mole Wheel
*Finding the Molar mass (AKA: Molecular Mass or Gram formula mass): the molar mass is the total mass of all of the elements
present in a compound. *Remember to add the mass of the water in a hydrate. (Compound containing water)
Ex 1: Find the molecular mass of Na2CO3
Na 2 x 23 = 23
C 1 x 12 = 12
O 1 x 16 = 16
106 g/mole
Ex 2: Find the mass of CuSO4 · 5H2O
1 x 64
1 x 32
4 x 16
5 x 18
Cu
S
Hydrate
O
remember to add the water! H2O
=
=
=
=
64
32
64
90
250 g/mole
*Determining % Composition:
Use Table T for the formula
Total mass of element in compound x 100 = % composition of that element
molar mass of compound
Ex. Find the % composition of sulfur in H2SO4
(molar mass = 108 g/mole)
% sulfur = 32 g x 100 = 30%
108 g
*Determining Empirical Formula from % Composition
1. Assume 100 grams of the substance and change % to grams.
2. Change grams to moles.
3. Divide all by the smallest mole amount to get a whole number ratio.
(if there are any 0.5 numbers you MUST double ALL numbers)
Ex. What is the empirical formula of a compound that is 40% sulfur and 60% oxygen by mass?
40 g of sulfur 40 g
= 1.25 moles
32 g/mole
1.25 moles = 1
1.25 moles
60 g of oxygen 60 g
= 3.75 moles
16 g/mole
3.75 moles = 3
1.25 moles
Empirical formula = SO3
*Determining Molecular Formula (given molecular mass and empirical formula)
1. Find the empirical mass.
2. Molecular Mass
3. Multiply empirical formula by the number found in step 2.
Empirical Mass
Ex. If the molecular mass of a compound is 58 g and the empirical formula is C2H5
what is the molecular formula?
2. 58 g = 2
1. C2H5 = 29 g
3. 2 x C2H5 = C4H10
29 g
*Using Gas Density to find the Molecular Mass
Density = molar mass of a GAS at STP
22.4 L
Vocabulary
diatomic element
mole
Avogadro’s number
hydrate
gram formula mass /Molar mass
percent composition
coefficient
gas density
empirical formula
JHS chemistry Department ~ Mole Concept & Mole Conversions 15-16
molecular formula
atomic mass
hydrate
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PERIOD:______________
Mole concept Homework
A. Basics of the Mole and chemical compounds
A. For each of the following compounds, find the number of atoms of each element present and calculate the molar mass.
Show all work!
Chemical Formula
Total Number of
Molar Mass (formula mass, gram formula mass)
moles of Atoms
SHOW ALL WORK
Ag2CO3
Ag = 2
276g
C = 1
O = 3
6 atoms
Fe(NO3)2
Fe = 1
N =2
O =6
9 atoms
180g
Na2S2O3 · 5 H2O
Na = 2
S =2
O =2
H = 10
O =5
21 atoms
248g
Page 338 #62
a)
108 g
b)
c)
71.8 g
d)
547 g
e)
224 g
f)
238 g
B. MOLE CONVERSIONS
Convert the following values using mole conversion techniques.
Convert from
Show all Work!
0.438 moles of NH4Cl
1.88 g
Convert to
23.9 Grams
0.849 grams of
Magnesium
.035 Moles
JHS chemistry Department ~ Mole Concept & Mole Conversions 15-16
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NAME: ________________________________
PERIOD:______________
1.9 moles of
fluorine gas
42.6 Liters
44.8 liters of
nitrogen gas
2 Moles
24
1.505 x 10 molecules
of carbon dioxide
2.5 Moles
1.5 mole (NH4)2S
102 Grams
3.2 moles of
CuSO4 · 5 H2O
798 Grams
3.01 x 1023 molecules of
Neon
11.2 Liters
3.01 x 1023 molecules of
O2
16 Grams
Text book:
Page 318 #17
Page 319 #19
225 g
.987 moles
Page 321
#20
#21
b) 82.9 L
c) 21.5 L
a) 3.00 moles
b) .0392 moles
JHS chemistry Department ~ Mole Concept & Mole Conversions 15-16
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NAME: ________________________________
PERIOD:______________
Page 338
#65
a) .258 moles
c) 1.12 moles
e) 5.93 moles
#67
b) 30.0 L
d) .0549 L
C. Percent Composition & Compound basics
Complete the questions for all of the following compounds. SHOW ALL WORK!
1.) CuBr2
a) state the IUPAC name for the compound: Copper (II) Bromide
b) State the type of bond in the compound: Ionic
c) Which of the elements in the compound is isoelectronic with Krypton: Br
d) Draw the Lewis structure for the compound:
e) Find the percent composition of the following elements in the compound:
2.)
percent Cu 28%
percent Br 72%
63.5/223.5 x 100
160/223.5 x 100
(NH4)3Cl
a) state the IUPAC name for the compound: Ammonium Chloride
b) State the type of bond(s) in the compound: Ionic & Covalent
c) Which of the elements in the compound is isoelectronic with Argon: Cl
d) Draw the Lewis structure for the NH4+ polyatomic ion
e) Find the percent composition of the following elements in the compound:
percent NH4 34%
percent Cl 66%
18/53.5 x 100
35.5/53.5 x 100
JHS chemistry Department ~ Mole Concept & Mole Conversions 15-16
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NAME: ________________________________
3.) CoCl2·6H2O
PERIOD:______________
a. state the IUPAC name for the compound: Cobalt (II) Chloride Hexahydrate
b. What element contributes to this compound being colored: Cu
c. What type of bond is found in CoCl2 Ionic
d. What type of bond is found in H2O Covalent
e. Draw the Lewis structure for H2O
b) Find the percent composition of the following elements in the compound:
percent H2O 45%
108/238 x 100
page 326
#33
#34
72.2 % Mg
#35
27.8% N
a) 82.4% N
7% O
93% Hg
b) 35%
Page 339 #75
a)
b)
c)
d) 77.7% Fe
D. Empirical & Molecular Formulas
Page 331
#39 a) H O
b) HgSO4
JHS chemistry Department ~ Mole Concept & Mole Conversions 15-16
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PERIOD:______________
Page 331 #40
C3H8N
Page 333
#41
C3Cl3N
#42
C2H6O2
#49
C5H10O2 is both the empirical and molecular formula
Page 339
#76 An empirical formula has the lowest whole number ratio of elements
C & D are both molecular and empirical formulas
#77
C
Page 340
#89
b) C6H6O4
c) K2CO3
#92
a) CuBr2
JHS chemistry Department ~ Mole Concept & Mole Conversions 15-16
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PERIOD:______________
E. Calculating Density
Page 322
#22
#23
80.2 g/mole
3.74 g/L
Page 323
#29 the balloons have the same number of molecules. Each balloon is filled with 1 mole of gas and 1 mole of any gas has
the same number of molecules. The masses of the balloons will be different.
#30
#31
a) 28.0 g
39.9 g/mole
b) 64.1 g
c) 16.0 g
F. Review
Page 343
#2 C
#9
A
#6 C
#4 B
#10 D
#8 E
#5 A
JHS chemistry Department ~ Mole Concept & Mole Conversions 15-16
#11 C
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JHS chemistry Department ~ Mole Concept & Mole Conversions 15-16
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