Lesson 2 Molar Quantities Read pages: 55-57 HW – More Mole Problems – Yuk.
1 Chapter 5 Chemical Quantities and Reactions 5.2 Molar Mass Copyright © 2009 by Pearson Education,...
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Transcript of 1 Chapter 5 Chemical Quantities and Reactions 5.2 Molar Mass Copyright © 2009 by Pearson Education,...
1
Chapter 5 Chemical Quantities and Reactions
5.2Molar Mass
Copyright © 2009 by Pearson Education, Inc.
2
Molar Mass
The molar mass
• is the mass of 1 mole of an element or compound.
• is the atomic or molecular mass expressed in grams.
Copyright © 2009 by Pearson Education, Inc.
3
Molar Mass from Periodic Table
Molar mass is the atomic mass expressed in grams.
1 mole of Ag 1 mole of C 1 mole of S = 107.9 g = 12.01 g = 32.07 g
Copyright © 2009 by Pearson Education, Inc.
4
Give the molar mass for each (to the tenths decimal
place).
A. 1 mole of K atoms = ________
B. 1 mole of Sn atoms = ________
Learning Check
5
Give the molar mass for each (to the tenths decimal
place).
A. 1 mole of K atoms = 39.1 g
B. 1 mole of Sn atoms = 118.7 g
Solution
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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 40.1 g/mole 40.1 g
Cl 2 35.5 g/mole 71.0 g
CaCl2 111.1 g
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Molar Mass of K3PO4
Calculate the molar mass of K3PO4.
Element Number of Moles
Atomic Mass Total Mass in K3PO4
K 3 39.1 g/mole 117.3 g
P 1 31.0 g/mole 31.0 g
O 4 16.0 g/mole 64.0 g
K3PO4 212.3 g
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Some 1-mole Quantities
32.1 g 55.9 g 58.5 g 294.2 g 342.2 g
One-Mole Quantities
Copyright © 2009 by Pearson Education, Inc.
11
A. K2O 94.2 g/mole
2 moles of K (39.1 g/mole) + 1 mole of O (16.0 g/mole) 78.2 g + 16.0 g = 94.2 g
B. Al(OH)3 78.0 g/mole
1 mole of Al (27.0 g/mole) + 3 moles of O (16.0 g/mole) + 3 moles of H (1.01 g/mole) 27.0 g + 48.0 g + 3.03 g = 78.0 g
Solution
12
Prozac, C17H18F3NO, is an antidepressant that inhibits the uptake of serotonin by the brain. What is the molar mass of Prozac?
1) 40.1 g/mole2) 262 g/mole 3) 309 g/mole
Learning Check
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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?
3) 309 g/mole
17 C (12.0) + 18 H (1.01) + 3 F (19.0) + 1 N (14.0)
+ 1 O (16.0) =
204 g C + 18.2 g H + 57.0 g F + 14.0 g N + 16.0 g
O = 309 g/mole
Solution
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Molar mass conversion factors • are fractions (ratios) written from the molar mass.• relate grams and moles of an element or compound.• for methane, CH4, used in gas stoves and gas heaters
is1 mole of CH4 = 16.0 g (molar mass
equality)
Conversion factors:
16.0 g CH4 and 1 mole CH4
1 mole CH4 16.0 g CH4
Molar Mass Factors
15
Acetic acid, C2H4O2, gives the sour taste to vinegar. Write two molar mass conversion factors for acetic acid.
Learning Check
Copyright © 2009 by Pearson Education, Inc.
16
Calculate molar mass for acetic acid C2H4O2:
24.0 g C + 4.04 g H + 32.0 g O = 60.0 g/mole C2H4O2
1 mole of acetic acid = 60.0 g acetic acid
Molar mass factors:1 mole acetic acid and 60.0 g acetic acid 60.0 g acetic acid 1 mole acetic acid
Solution
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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 mole of Al?
Molar mass equality: 1 mole of Al = 27.0 g of Al
Setup with molar mass as a factor:
3.00 mole Al x 27.0 g Al = 81.0 g of Al1 mole Al
molar mass factor for Al
Moles to Grams
19
Learning Check
Allyl sulfide, C6H10S, is a compound that has the odor of garlic. How many moles of C6H10S are in 225 g?
Copyright © 2009 by Pearson Education, Inc.
20
Calculate the molar mass of C6H10S.
(6 x 12.0) + (10 x 1.01) + (1 x 32.1) = 114.2 g/mole
Set up the calculation using a mole factor.
225 g C6H10S x 1 mole C6H10S
114.2 g C6H10S
molar mass factor (inverted)
= 1.97 moles of C6H10S
Solution
22
Learning Check
How many H2O molecules are in 24.0 g of H2O?
1) 4.52 x 1023 H2O molecules
2) 1.44 x 1025 H2O molecules
3) 8.03 x 1023 H2O molecules
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Solution
How many H2O molecules are in 24.0 g of H2O?
3) 8.02 x 1023
24.0 g H2O x 1 mole H2O x 6.02 x 1023 H2O molecules 18.0 g H2O 1 mole H2O
= 8.03 x 1023 H2O molecules
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Learning Check
If the odor of C6H10S can be detected from 2 x 10-13 g in 1 liter of air, how many molecules of C6H10S are present?