# moles = grams molar mass

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```Chapter 7
The Mole
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M 11-17 Rev test, Rev mole, atomic mass isotop
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B-1 11/18-19 Molar mass, % comp
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B-2 11/20-1 Quiz Mass/Mol #/part. , emp form
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Mon/Tues 11/24 B-1 Lab Emp Form
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Mon 12/1 12/1 Rev Lab, Emp Form/Molec Form
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B-1 12/2-3 Quiz (g mol # part) Bal Chem Eq
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B-2 12/4-5 Rx Types
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M 12/8 Review
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B-1 12/9-10 Test
Math prob in the text
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Atomic mass determination (#42-44 pg 253)
Molar mass from formula (45-48 p 253)
g to mol to # particles (19-41 p 253)
% composition (55-57 p 253)
Empirical formula (49-50 p 253)
Molecular formula (45-54 p 253)
Collection Terms
1 trio
=
3 singers
1 ream paper
=
500 sheets
1 dozen donuts
=
12 donuts
1 gross of pencils
=
144 pencils
A Moles of Particles
Contains 6.02 x 1023 particles
1 mole C
= 6.02 x 1023 C atoms
1 mole H2O = 6.02 x 1023 H2O molecules
1 mole NaCl = 6.02 x 1023 Na+ ions and
6.02 x 1023 Cl– ions
Examples of Moles
Moles of elements
1 mole Mg = 6.02 x 1023 Mg atoms
1 mole Au = 6.02 x 1023 Au atoms
Moles of compounds
1 mole NH3= 6.02 x 1023 NH3 molecules
1 mole C9H8O4 = 6.02 x 1023 aspirin molecules
Avogadro’s Number
6.02 x 1023 particles
1 mole
or
1 mole
6.02 x 1023 particles
Learning Check
Suppose we invented a new collection unit
called a mep. One mep contains 8 objects.
A. How many paper clips in 1 mep?
1) 1
2) 4
3) 8
B. How many oranges in 2.0 meps?
1) 4
2) 8
3) 16
C. How many meps in 40 gummy bears?
1) 5
2) 10
3) 20
Solution
Suppose we invented a new collection unit
called a mep. One mep contains 8 objects.
A. How many paper clips in 1 mep?
3) 8
B. How many oranges in 2.0 meps?
3) 16
C. How many meps in 40 gummy bears?
1) 5
Learning Check
1. Number of atoms in 0.500 mole of Al
1) 500 Al atoms
2) 6.02 x 1023 Al atoms
3) 3.01 x 1023 Al atoms
2.Number of moles of S in 1.8 x 1024 S atoms
1) 1.0 mole S atoms
2) 3.0 mole S atoms
3) 1.1 x 1048 mole S atoms
Solution
1. Number of atoms in 0.500 mol of Al
0.500 mol Al x 6.02 x 1023 Al atoms = # Atoms
3) 3.01 x 1023 Al atoms
2. Number of moles of S if a sample of S
contains 4.50 x 1024 S atoms
4.50 x 1024 S atoms
= moles
6.02 x 1023 S atoms/mol
2) 7.48 mole S atoms
Molar Mass of Elements
remember these are atoms


Number of grams in 1 mole of atoms
Equal to the numerical value of the
atomic mass from the periodic table
1 mole of C atoms
=
12.0 g
1 mole of Mg atoms
=
24.3 g
1 mole of Cu atoms
=
63.5 g
Learning Check
Give the molar mass to 1.0 mole
A. 1 mole of Br atoms
________
=
B. 1 mole of Sn atoms
________
=
Atomic Mass Determination

How many grams in 10 moles of H2O?

How many grams in 1.0 mol of H2SO4?
Molar Mass Determination

How many grams in 1.0 mol of CaSO4?

How many grams in 1.0 mol of Ca(NO3)2?
Solution
A. 1 mole of Br atoms =
79.9 g/mole
B. 1 mole of Sn atoms =
118.7 g/mole
Atomic Mass Determination




What is this number 35.453 for Cl??
The atomic mass - the average mass of all the
isotopes (diff atoms) that make up a sample of
chlorine
Chlorine consists of 75.77% chlorine-35 (mm =
34.968853 amu) and 24.23% chlorine-37
(36.965903 amu)
Atomic Mass is an average based on the
percents and masses of each of the isotopes
of chlorine
Mass spectrometer
Atomic Mass Determination

Atomic mass =

(abundiso1 x mass iso1) + (abund
iso2
x mass iso2) +…
Atomic Mass Determination

Chlorine consists of 75.77% chlorine-35
(mm = 34.968853 amu) and 24.23% chlorine-37
(36.965903 amu)
1: convert the percentage to a decimal:
0.7577 chlorine-35
0.2423 chlorine-37
2: 0.7577 x 34.968853 amu = 26.4958992 amu
0.2423 x 36.965903 amu = 8.9651 amu
35.4527 amu
Atomic Mass Determination

Nitrogen consists of two naturally
occurring isotopes



99.63% nitrogen-14 with a mass of
14.003 amu
0.37% nitrogen-15 with a mass of 15.000
amu
What is the atomic mass of nitrogen?
An imaginary element has three naturallyoccurring isotopes with isotopic weights of
92.9469, 93.2923 and 94.9030. The
abundance of the isotopes are 42.38 %, 31.44
% , and 26.18 %. What is the atomic mass of
the element?
Molar Mass of Compounds
Give the molar mass to 0.1 g
1 mole of CaCl2 formula units = ? g/mole
1 mole of N2O4 molecules = ? g/mole
Molar Mass of Compounds
Both molecules and Ionic Compounds
Mass in grams of 1 mole is equal to the sum of
the atomic masses of all the atoms present
1 mole CaCl2 =
(1 mole Ca x 40.1 g/mole) + (2 moles Cl x 35.5 g/mole)
1 mole of CaCl2
= 111.1 g/mole
1 mole N2O4 =
(2 moles N x 14.0 g/mole) + (4 moles O x 16.0 g/mole)
1 mole of N2O4
= 92.0 g/mole
Learning Check
A. 1 mole of K2O = ______g
B. 1 mole of antacid Al(OH)3 = ______g
Solution
A. 1 mole of K2O
(2 K x 39.1 g/mole) + (1 O x 16.0 g/mole) = 94.2 g
B. 1 mole of antacid Al(OH)3
(1 Al x 27.0 g/mol) +(3 O x 16.0 g/mol) + (3 H x 1.0) = 78.0 g
Molar Mass of Compounds
Both molecules and Ionic Compounds
Mass in grams of 1 mole is equal to the sum of the
atomic masses of all the atoms present
(1 mole Ca x 40.1 g/mole) + (2 moles Cl x 35.5 g/mole)
1 mole of CaCl2 = 111.1 g/mole
(2 moles N x 14.0 g/mole) + (4 moles O x 16.0 g/mole)
1 mole of N2O4 = 92.0 g/mole
Learning Check
Prozac, C17H18F3NO, is a widely used
antidepressant that inhibits the uptake of
serotonin by the brain. It has a molar mass of
1) 40.0 g/mole
2) 262 g/mole
3) 309 g/mole
Solution
Prozac, C17H18F3NO, is a widely used
antidepressant that inhibits the uptake of
serotonin by the brain. It has a molar mass of
17C (12.0) + 18H (1.0) + 3F (19.0) + 1N (14.0) + 1 O (16.0)
= 309 g/mole
Calculate the molar mass of
C16H18N2O4S = penicillin
(NH4)3PO4
Thallium-203 has a molar mass of 202.9723 g/mol
and a relative abundance of 29.52%. Thallium-205
has a molar mass of 204.9744 g/mol and a relative
abundance of 70.48%. What is the average atomic
mass of Thallium?
Determine the percent
composition of H2SO4



1 – Calc the # grams in a mole of the
formula
2 – Divide each of the elements total
masses by the molar mass
3 – Mult by 100 to make a percent
Determine the percent
composition of H2SO4

H 2 x 1.0 g

S 1 x 32.1 g

O 4 x 16.0 g
= 2.0 g x 100 =
98.1
= 32.1 g x 100 =
98.1
= 64.0 g x 100 =
98.1 g/mol
What is the percent composition of
C5H8NO4 MSG, a compound used to flavor
foods and tenderize meats?
What is the percent
composition of Ca(NO3)2
Calculations with Molar Mass
grams = molar mass
moles
grams
= moles
molar mass
molar mass x
moles = grams
Calculations with Molar Mass
grams = molar mass
moles
grams
=
moles
molar mass
molar mass x moles = grams
# Atoms etc
=
moles
(# atoms, ions, or molecules)
Avo #
moles x Avo # = # Atoms etc
Grams to # particles

Grams
moles
# Particles
Mole to Grams





Moles =
grams
or
molar mass
Grams = moles x molar mass
How many moles in 27.0 g NaCl?
How many grams in 0 .575 moles H2O?
Moles = grams/molar mass




Determine the number of moles in 27.35 g of the
element sulfur.
Calculate the number of moles of SiO2 in a 18.95 g
sample
Moles = grams/molar mass


Determine the number of grams in 0.0595 moles
of H2O ( mm = 18.0 g/mol)?
Determine the number of grams in 1.83 x 10-3
moles of SiO2 (SiO2 mm = 60.1 g/mol)
Learning Check
The artificial sweetener aspartame
(Nutri-Sweet) formula C14H18N2O5
is used to sweeten diet foods,
coffee and soft drinks. How many
moles of aspartame are present in
225 g of aspartame?
Solution
Molar mass of Aspartame C14H18N2O5
(14 x 12.0) + (18 x 1.0) + (2 x 14.0) + (5 x 16.0)
= 294.0 g/mole
moles
=
grams
molar mass
Setup
moles = 225 g aspartame
= 0.765 mol
294.0 g aspartame/mol
Moles to # Particles
# Atoms = moles x Avo #
moles = # Atoms
Avo #
How many moles in 6.14 x 1025 atoms of Au?

How many atoms are there in 10.2 moles ofAr ?
Grams to # particles


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
Grams
moles
# Particles
One or two steps can be used to solve this:
6.02 x 1023 atoms
molar mass (grams)
molar mass (grams)
6.02 x 1023 atoms


Determine the number of atoms in 27.35 g
of the element sulfur (S mm = 32.1 g/mol).
Determine the number of grams in 5.95 x
1025 molecules of H2O ( mm = 18.0 g/mol)?
How many grams in 1000 Au atoms?

Solution
Molar mass = 146.0 g/mole
%=
total g C
x 100
total g compound
=
60.0 g C
146.0 g MSG
x 100 = 41.1% C
Molar Mass Factors
Methane CH4 known as natural gas is used
in gas cook tops and gas heaters. Express
the molar mass of methane in the form of
conversion factors.
Molar mass of CH4 =
16.0 g CH4
1 mole CH4
and
16.0 g
1 mole CH4
16.0 g CH4
Learning Check
Acetic acid CH3COOH is the acid in vinegar
. It has a molar mass of 60.0 g/mole.
1 mole of acetic acid
1 mole acetic acid
g acetic acid
=
____________
or
g acetic acid
1 mole acetic acid
Solution
Acetic acid CH3COOH is the acid in vinegar . It
has a molar mass of 60.0 g/mole.
1 mole of acetic acid
1 mole acetic acid
60.0 g acetic acid
=
or
60.0 g acetic acid
60.0 g acetic acid
1 mole acetic acid
Moles and Grams
Aluminum is often used for the
structure of light-weight bicycle
frames. How many grams of Al are in
3.00 moles of Al?
3.00 moles Al
? g Al
Mole Mass Conversions
(grams = mol x molar mass)
Setup
grams = mol x molar mass
3.00 moles Al x 27.0 g Al
= 81.0 g Al
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