Mastering Chemical Calculations with Moles
•
Homework 4 Due Today
•
Keep Reading Chapter 5
•
Homework 5 posted and due this Friday 20 October
Interim Grades Issued this week !
We’re half-way through !!!
Hang tough to the end `
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5
Students should be able to
perform
basic chemical calculations connected to:
•
mole-weight-count conversions
•
reaction stoichiometry
•
limiting yields.
From your lecture syllabus….
Translation:
How do chemists count atoms
and molecules without actually
having to count them ???
Chemists count
atoms and
molecules using…
Moles
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The
mole
: starting definitions
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Not that helpful when first starting out…
A better beginning:
the
mole concept
is really
…
the same idea as a
`dozen.’
IN-CLASS EGG CALCULATIONS
EGG
WORLD
CHEMISTRY
WORLD
Smallest
unit
Practical
Counting
unit
Dozen
1 egg
1 molecule
Mole
(The chemist’s dozen)
EGG
WORLD
CHEMISTRY
WORLD
grams/dozen
(WEIGH)
Practical
mass unit
# units in
practical
counting unit
1 dozen=12
1 mole
6.022 *10
23
grams/mole
=gram molecular weight
= MW
(molecular weight)
(ADD)
(Avogadro’s #)
Eggs vs. chemistry world (continued)
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box of eggs
Just add up atomic masses
using Periodic Table in
grams
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Example of
MW
Calculation:
What is the
MW
of
methane =CH
4
??
C
H
atomic mass (Table)
12.011~12
1.00794~1
# atoms/molecule
1
4
product
~12*1=12
~
1*4 = 4
Sum =
MW
= 12+4=16 g/mole
In – class exercise on Molecular Weight (
MW
)
calculations
H
2
SO
4
2
*1 +
1
*32 +
4
*16 =
98 g/mol
Find the
MW
of…
In – class exercise on Molecular Weight (
MW
)
calculations (continued)
CaCl
2
1
*40 +
2
*35.4 =
110.4 g/mol
Find the
MW
of…
In – class exercise on Molecular Weight (
MW
)
calculations (continued)
Cu
3
(PO
4
)
2
3
*63.5 +
2
*(
1
*31 +
4
*16) =
380.5 g/mol
Find the
MW
of…
In – class exercise on Molecular Weight (
MW
)
calculations (continued)
Find the
MW
of…
CaCl
2
*
2
H
2
O
1
*40 +
2
*35.4 +
2
*(
2
*1 +
1
*16)
=
146.8 g/mol
2
`waters of hydration’ per CaCl
2
IN-CLASS simple mole calculations
(on board) the dozen method way
moles
Molecule count
weight
The triangle `trick’ for those allergic to eggs
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Divide up
Multiply Down
MW
6.0*10
23
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the dozen concept is really the triangle trick
# of dozens
# of eggs (count)
Weight of eggs
1000 g
1 dozen eggs
12 eggs in a
dozen
Given
6000 g
of eggs= ????
dozens
6000 grams
DIVIDE UP: 6000/
1000
=
6
6
the dozen concept is really the triangle trick
# of dozens
# of eggs (count)
Weight of eggs
1000 g
1 dozen eggs
12 eggs in a
dozen
Given
6000 g
of eggs= ????
# eggs ?
6000 grams
6
Multiply down
6*12=72
72 g
On the triangle…,.
DIVIDE UP
MULTIPLY DOWN
IN-CLASS simple mole calculations
(on board) the triangle trick way
MORE “Sweet” Mole Calculations:
but first a public service message
Sucrose
2
glucose
C
11
H
22
O
11
2
C
6
H
12
O
6
In Coke
What your body burns
The result of steady Coke drinking……
Obese=> BMI > 30
(~30-35 lbs over weight)
Children
circa 1955
Children
circa 2016
Reported US Diabetes Diagnoses vs. year
a)
weight per mole (MW):
what does a mole
of C
6
H
12
O
6
weigh ? (C=12; H=1; O=16)
6*12 + 12*1 + 6*16 =
180 g/mol
1.1) mole to mass:
how many g C
6
H
12
O
6
of
are present in 0.00555 mole of C
6
H
12
O
6
?
0.00555 mol * 180 g/mol =
1 g
1.2) mass to mole:
how many moles of C
6
H
12
O
6
are in 360 g of C
6
H
12
O
6
?
Sweet mole calculations part 1
360 g/180 g mol
-1
=
2 moles
mole calculations part 1 (continued)
1.3)
mole to # molecule:
how many molecules
of C
6
H
12
O
6
are in 0.5 mol of C
6
H
12
O
6
?
0.5 mol *6*10
23
molecules/mol =
3*10
23
molecules
1.4) mass to # molecules:
how many molecules of
C
6
H
12
O
6
are in 120 g of C
6
H
12
O
6
?
(
120/180) mol * 6*10
23
molecules
=
4*10
23
molecules
mol
1.5) # molecules to moles:
how many moles in
3*10
24
molecules of
C
6
H
12
O
6
?
3*10
24
molecules/ 6*10
23
molecules/mol
=
5 moles
1.6) # molecules to mass
: How many grams of
C
6
H
12
O
6
are in 2.0 *10
22
molecules of C
6
H
12
O
6
?
2*10
22
molecules
*
180 g
6*10
23
molecules/mol mol
=0.0333 * 180 =
6 grams
mole calculations part 1 (continued)
Harder problems….team
efforts with clickers
A.
7.27*10
21
B.
0.0121
C.
82.9
D.
2.48*10
-22
E.
My answer isn’t above
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A.
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g
B.
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C.
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g
D.
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-10
g
E.
Not any of above
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2
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A.
5.4*10
24
B.
3.5*10
22
C.
3.2*10
11
D.
5.3*10
22
Transition into the fascinating world of chemical calculations using moles to count atoms and molecules without tedious counting. Explore concepts like Avogadro's number, practical counting units, and the significance of the mole in chemistry. Dive deep into the connections between atomic and human scales through inventive analogies and real-world applications. Enhance your understanding of reaction stoichiometry, limiting yields, and more as you progress through your chemistry journey.
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Presentation Transcript
Homework 4 Due Today Keep Reading Chapter 5 Homework 5 posted and due this Friday 20 October Interim Grades Issued this week ! We re half-way through !!! Hang tough to the end `
From your lecture syllabus. Student Learning Outcome 5 Students should be able to perform basic chemical calculations connected to: mole-weight-count conversions reaction stoichiometry limiting yields. Translation: How do chemists count atoms and molecules without actually having to count them ??? http://t2.gstatic.com/images?q=tbn:ANd9GcTIy_ERVxFIOF2NsBNlSEUDApyXhu2BXMlXWryX7HwL5JBaQA4Y
Chemists count atoms and molecules using Moles
A trip to Mole land A trip to Mole land Moles connect the atomic world to human world ~ 1027 molecules in the shape of a couch potato ~0.00000002m ~2m ~30 CO2 molecules arranged in Moles allow us to conveniently connect between these worlds using a scale. shape of muffin man (IBM)
The mole: starting definitions What is a chemical mole ? The classic textbook rant .(but not your text s rant, fortunately) # atoms in 12.000 g of 12C 6.0221335 *1023 atoms (Avogadro s Number) Not that helpful when first starting out
A better beginning: the mole concept is really the same idea as a `dozen.
EGG WORLD Smallest unit CHEMISTRY WORLD 1 egg 1 molecule Practical Counting unit Mole Dozen (The chemist s dozen)
Eggs vs. chemistry world (continued) EGG WORLD CHEMISTRY WORLD # units in practical counting unit 1 mole 6.022 *1023 (Avogadro s #) 1 dozen=12 grams/mole =gram molecular weight = MW (molecular weight) (ADD) Practical mass unit grams/dozen (WEIGH)
THE ONE PLACE THE ONE PLACE EGG WORLD TEENY BIT TEENY BIT: : EGG WORLD AND AND CHEMISTRY WORLD CHEMISTRY WORLD DEVIATE A DEVIATE A Egg world Chemistry world Mass dozen Mass = molecular weight mol Just add up atomic masses using Periodic Table in grams (MW) Must weigh box of eggs
Mass (grams) = MW=Molecular mol Weight = sum of masses in grams of component elements in a compound . (element masses are average masses taken from Periodic Table)
Example of MW Calculation: What is the MW of methane =CH4 ?? atomic mass (Table) # atoms/molecule 1 4 product ~12*1=12 ~1*4 = 4 C H 12.011~12 1.00794~1 Sum = MW = 12+4=16 g/mole
In class exercise on Molecular Weight (MW) calculations Find the MW of H2SO4 2*1 + 1*32 + 4*16 = 98 g/mol
In class exercise on Molecular Weight (MW) calculations (continued) Find the MW of CaCl2 1*40 + 2*35.4 = 110.4 g/mol
In class exercise on Molecular Weight (MW) calculations (continued) Find the MW of Cu3(PO4)2 3*63.5 + 2*(1*31 +4*16) = 380.5 g/mol
In class exercise on Molecular Weight (MW) calculations (continued) Find the MW of CaCl2*2H2O 2 `waters of hydration per CaCl2 1*40 + 2*35.4 + 2*(2*1 + 1*16) =146.8 g/mol
IN-CLASS simple mole calculations (on board) the dozen method way
The triangle `trick for those allergic to eggs moles weight Molecule count
Multiply Down Moles (n) 6.0*1023 MW ALL ROADS LEAD THROUGH MOLES Weight (w) molecule count (N) Divide up
the dozen concept is really the triangle trick Given 6000 g of eggs= ???? dozens 6 # of dozens 1000 g 1 dozen eggs 12 eggs in a dozen # of eggs (count) Weight of eggs 6000 grams DIVIDE UP: 6000/1000=6
the dozen concept is really the triangle trick Given 6000 g of eggs= ???? # eggs ? 6 Multiply down 6*12=72 # of dozens 1000 g 1 dozen eggs 12 eggs in a dozen # of eggs (count) 72 g Weight of eggs 6000 grams
On the triangle,. DIVIDE UP MULTIPLY DOWN
IN-CLASS simple mole calculations (on board) the triangle trick way
MORE Sweet Mole Calculations: but first a public service message Sucrose C11H22O11 2 C6H12O6 In Coke 2 glucose What your body burns
Obese=> BMI > 30 (~30-35 lbs over weight)
Children circa 1955 Children circa 2016
Sweet mole calculations part 1 a) weight per mole (MW): what does a mole of C6H12O6 weigh ? (C=12; H=1; O=16) 6*12 + 12*1 + 6*16 = 180 g/mol 1.1) mole to mass: how many g C6 H12O6 of are present in 0.00555 mole of C6 H12O6? 0.00555 mol * 180 g/mol = 1 g 1.2) mass to mole: how many moles of C6 H12O6 are in 360 g of C6H12O6? 360 g/180 g mol-1 = 2 moles
mole calculations part 1 (continued) 1.3) mole to # molecule: how many molecules of C6 H12O6 are in 0.5 mol of C6H12O6 ? 0.5 mol *6*1023 molecules/mol = 3*1023 molecules 1.4) mass to # molecules: how many molecules of C6 H12O6 are in 120 g of C6H12O6 ? (120/180) mol * 6*1023 molecules =4*1023 molecules mol
mole calculations part 1 (continued) 1.5) # molecules to moles: how many moles in 3*1024 molecules of C6 H12O6 ? 3*1024 molecules/ 6*1023 molecules/mol = 5 moles 1.6) # molecules to mass : How many grams of C6 H12O6 are in 2.0 *1022 molecules of C6 H12O6 ? 2*1022 molecules * 180 g 6*1023 molecules/mol mol =0.0333 * 180 = 6 grams
Harder problems.team efforts with clickers
The gram molecular mass of of The gram molecular mass of of crystal meth many moles of crystal meth are in a typical street `teenth = 1/16 of many moles of crystal meth are in a typical street `teenth = 1/16 of an ounce= 1.80 grams ? an ounce= 1.80 grams ? ( (1 mol count=6.0*10 1 mol count=6.0*1023 crystal meth ) ) is is 149.2 g/mol. 149.2 g/mol. How How 23 .) .) 94% A. 7.27*1021 B. 0.0121 C. 82.9 D. 2.48*10-22 E. My answer isn t above 6% 0% 0% 0% 82.9 0.0121 7.27*1021 2.48*10-22 My answer isn t above
B1 B1- -Aflatoxin (MW=328.2 g/mol) Aflatoxin (MW=328.2 g/mol) is a naturally occurring, horribly toxic poison is a naturally occurring, horribly toxic poison derived from Aspergillus fungi, a common contaminant in corn. It causes cancer in derived from Aspergillus fungi, a common contaminant in corn. It causes cancer in most humans at the staggeringly low exposure level of 1*10 most humans at the staggeringly low exposure level of 1*1017 the equivalent mass of aflatoxin represented by this count ? the equivalent mass of aflatoxin represented by this count ? ( ( 1 mol count=6.0*10 count=6.0*1023 17 molecules. What is molecules. What is 1 mol 23 .) 58% A. 3.3*10-8 g B. 1.8*10-4 g C. 5.47*10-5g D. 5.06*10-10g E. Not any of above 26% 16% 0% 0% 5.47*10-5g 5.06*10-10g 3.3*10-8 g 1.8*10-4 g Not any of above
Micro chip manufacture requires nearly oxygen Micro chip manufacture requires nearly oxygen- -free conditions wherein the concentration of wherein the concentration of O O2 2 is at or below 17 pg/L. Given that the atomic mass of that the atomic mass of O O is is 16 16 g/mol, g/mol, about how many molecules of molecules of O O2 2 /L /L does this represent ? does this represent ? Note: 1 mol count=6.0*10 count=6.0*1023 free conditions is at or below 17 pg/L. Given about how many Note: 1 mol 23 A. 5.4*1024 B. 3.5*1022 C. 3.2*1011 D. 5.3*1022 94% 6% 0% 0% 5.4*1024 3.5*1022 3.2*1011 5.3*1022
