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Transcript of Chapter 7 Chemical Quantities Copyright © 2005 by Pearson Education, Inc. Publishing as Benjamin...
![Page 1: Chapter 7 Chemical Quantities Copyright © 2005 by Pearson Education, Inc. Publishing as Benjamin Cummings.](https://reader037.fdocuments.in/reader037/viewer/2022102713/56649ebb5503460f94bc2c49/html5/thumbnails/1.jpg)
Chapter 7 Chemical Quantities
Copyright © 2005 by Pearson Education, Inc.Publishing as Benjamin Cummings
![Page 2: Chapter 7 Chemical Quantities Copyright © 2005 by Pearson Education, Inc. Publishing as Benjamin Cummings.](https://reader037.fdocuments.in/reader037/viewer/2022102713/56649ebb5503460f94bc2c49/html5/thumbnails/2.jpg)
Atomic Mass
Atomic mass is the• Mass of a single
atom in atomic mass units (amu)
• Mass of an atom compared to a 12C atom
• Number below the symbol of an element
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Periodic Table and Atomic Mass
Ag has atomic mass = 107.9 amu
C has atomic mass = 12.01 amu
S has atomic mass = 32.07 amu
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Atomic Mass Factors
The atomic mass, • Can be written as an equality
Example: 1 P atom = 30.97 amu
• Can be written as two conversion factors
Example:
1 P atom and 30.97 amu
30.97 amu 1 P atom
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Uses of Atomic Mass Factors
The atomic mass is used to convert:
• A specific number of atoms to mass (amu)
• An amount in amu to number of atoms
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Learning Check
What is the mass in amu of 75
silver atoms?
1) 107.9 amu
2) 8093 amu
3) 1.439 amuCopyright © 2005 by Pearson Education, Inc.Publishing as Benjamin Cummings
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Learning Check
How many gold atoms have a
mass of 1.85 x 105 amu?
1) 939 Au atoms
2) 3.64 x 107 Au atoms
3) 106 Au atomsCopyright © 2005 by Pearson Education, Inc.Publishing as Benjamin Cummings
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Formula Mass
The formula mass is• The mass in amu
of a compound• The sum of the
atomic masses of the elements in a formula
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Calculating Formula Mass
To calculate formula mass of Na2SO4,
• Multiply the atomic mass of each element by its subscript
• Total the masses
2 Na x 22.99 amu = 45.98 amu Formula mass
1 Na2SO4
1 S x 32.07 amu = 32.07 amu 142.05 amu1 S
4 O x 16.00 amu = 64.00 amu1 O
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Learning Check
Using the periodic table, calculate the formula mass of aluminum sulfide Al2S3.
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Collection Terms
A collection term states
a specific number of items.
• 1 dozen donuts
= 12 donuts
• 1 ream of paper
= 500 sheets
• 1 case = 24 cans
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A mole (mol) is a collection that contains:
• The same number of particles as there are carbon atoms in 12.01 g of carbon
• 6.022 x 1023 atoms of an element (Avogadro’s number).
1 Mol element Number of Atoms
1 mol C = 6.022 x 1023 C atoms
1 mol Na = 6.022 x 1023 Na atoms
1 mol Au = 6.022 x 1023 Au atoms
A Mole of Atoms
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A mole
• Of a covalent compound has Avogadro’s number of molecules
1 mol CO2 = 6.022 x 1023 CO2 molecules
1 mol H2O = 6.022 x 1023 H2O molecules
• Of an ionic compound contains Avogadro’s number of formula units
1 mol NaCl = 6.022 x 1023 NaCl formula units
1 mol K2SO4 = 6.022 x 1023 K2SO4 formula units
A Mole of a Compound
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Samples of One-Mole Quantities
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Avogadro’s number 6.022 x 1023 can be written as an
equality and two conversion factors.
Equality:
1 mol = 6.022 x 1023 particles
Conversion Factors:
6.022 x 1023 particles and 1 mol 1 mol 6.022 x 1023
particles
Avogadro’s Number
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Using Avogadro’s Number
Avogadro’s number is used to convert Moles of a substance to Particles.
How many Cu atoms are in 0.50 mol Cu?
0.50 mol Cu x 6.022 x 1023 Cu atoms 1 mol Cu
= 3.0 x 1023 Cu atoms
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Using Avogadro’s Number
Avogadro’s number is used to convert Particles of a substance to Moles.
How many moles of CO2 are in
2.50 x 1024 CO2 molecules?
2.50 x 1024 CO2 x 1 mol CO2
6.022 x 1023 CO2
= 4.15 mol CO2
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1. The number of atoms in 2.0 mol Al is
A. 2.0 Al atoms
B. 3.0 x 1023 Al atoms
C. 1.2 x 1024 Al atoms
2. The number of moles of S in 1.8 x 1024 atoms S is
A. 1.0 mol S atoms
B. 3.0 mol S atoms
C. 1.1 x 1048 mol S atoms
Learning Check
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Subscripts and Moles
The subscripts in a formula state• The relationship of atoms in the formula.• The moles of each element in 1 mol of compound.
Glucose
C6H12O6
In 1 molecule: 6 atoms C 12 atoms H 6 atoms O
In 1 mol: 6 mol C 12 mol H 6 mol O
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Subscripts State Atoms and Moles
The subscripts are used to write conversion factors formoles of each element in 1 mol compound. For aspirinC9H8O4, the following factors can be written:
9 mol C 8 mol H 4 mol O 1 mol C9H8O4 1 mol C9H8O4 1 mol C9H8O4
and
1 mol C9H8O4 1 mol C9H8O4 1 mol C9H8O4 9 mol C 8 mol H 4 mol O
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Learning Check
How many O atoms are in 0.150 mol aspirin C9H8O4?
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Molar Mass
The molar mass • Is the mass of one mole
of an element or compound
• Is the atomic mass expressed in grams
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Molar Mass from Periodic Table
Molar mass • Is the atomic
mass expressed in grams
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Molar Mass of a Compound
The molar mass of a compound is the sum of the molar masses of the elements in the formula.
Example: Calculate the molar mass of CaCl2.
Element Number of Moles
Atomic Mass Total Mass
Ca 1 40.08 g/mol 40.08 g
Cl 2 35.45 g/mol 70.90 g
CaCl2 110.98 g
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Some One-Mole Quantities
32.07 g 55.85 g 58.44 g 294.20 g 342.30 g
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Prozac, C17H18F3NO, is an antidepressant that inhibits the uptake of serotonin by the brain. What is the molar mass of Prozac?1) 40.06 g/mol2) 262.0 g/mol 3) 309.3 g/mol
Learning Check
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Molar mass conversion factors: • Are written from molar mass• Relate grams and moles of an element or compound.
Example: Write molar mass factors for methane CH4 used
in gas cook tops and gas heaters.
Molar mass:
1 mol CH4 = 16.04 g
Conversion factors:
16.04 g CH4 and 1 mol CH4
1 mol CH4 16.04 g CH4
Molar Mass Factors
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Acetic acid C2H4O2 gives the sour taste to vinegar. Write two molar mass conversion factors for acetic acid.
Learning Check
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Molar mass factors are used to convert between the grams of a substance and the number of moles.
Calculations Using Molar Mass
Grams Molar mass factor Moles
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Aluminum is often used to build lightweight bicycleframes. How many grams of Al are in 3.00 mol Al?
Molar mass equality: 1 mol Al = 26.98 g Al
Setup with molar mass as a factor:
3.00 mol Al x 26.98 g Al = 80.9 g Al1 mol Al
molar mass factor for Al
Moles to Grams
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Learning Check
Allyl sulfide C6H10S is a compound that has the odor of garlic. How many moles of C6H10S are in 225 g?
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Grams, Moles, and Particles
A molar mass factor and Avogadro’s number convert:• Grams to particles
molar mass Avogadro’s number
(g mol particles)
• Particles to grams
Avogadro’s number molar mass (particles mol g)
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Learning Check
How many H2O molecules are in 24.0 g H2O?
1) 4.52 x 1023
2) 1.44 x 1025
3) 8.02 x 1023
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Percent Composition
Percent composition
• Is the percent by mass of each element in a formula
Example: Calculate the percent composition of CO2.
CO2 = 1 C(12.01g) + 2 O(16.00 g) = 44.01 g/mol)
12.01 g C x 100 = 27.29 % C 44.01 g CO2
32.00 g O x 100 = 72.71 % O 44.01 g CO2 100.00 %
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Learning Check
The chemical isoamyl acetate C7H14O2 gives the odor of pears. What is the percent carbon in isoamyl acetate?
1) 7.102% C
2) 35.51% C
3) 64.58% C
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The molecular formula • Is the true or actual number of the atoms in a molecule
The empirical formula
• Is the simplest whole number ratio of the atoms
• Is calculated by dividing the subscripts in the molecular formula by a whole number to give the lowest ratio
C5H10O5 5 = C1H2O1 = CH2Omolecular empirical formula
formula
Types of Formulas
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Some Molecular and Empirical Formulas
• The molecular formula is the same or a multiple of the empirical.
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A. What is the empirical formula for C4H8?
1) C2H4 2) CH2 3) CH
B. What is the empirical formula for C8H14?
1) C4H7 2) C6H12 3) C8H14
C. Which is a possible molecular formula for CH2O?
1) C4H4O4 2) C2H4O2 3) C3H6O3
Learning Check
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A compound contains 7.31 g Ni and 20.0 g Br.
• Calculate its empirical (simplest) formula.
• If the compound has a molar mass of 437 g/mol, calculate the molecular formula.
Learning Check
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Aspirin is 60.0% C, 4.5% H and 35.5% O. Calculate its empirical (simplest) formula.
Learning Check