Transcript CH_5_2_Molar_Mass

Chapter 5
Chemical Quantities and Reactions
1
5.2
Molar Mass
Chemistry An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition
Copyright © 2012 by Pearson Education, Inc.
Molar Mass
2
The molar mass
• is the mass of 1 mole of an element
• is the atomic mass expressed in grams
Chemistry An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition
Copyright © 2012 by Pearson Education, Inc.
Molar Mass from Periodic Table
3
Molar mass is the atomic mass expressed in grams.
1 mole of Ag
= 107.9 g of Ag
1 mole of C
= 12.0 g of C
1 mole of S
= 32.1 g of S
Chemistry An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition
Copyright © 2012 by Pearson Education, Inc.
Learning Check
4
Give the molar mass for each element (to the tenths place).
A. 1 mole of K atoms
=
________
B. 1 mole of Sn atoms
=
________
C. 1 mole of Ca atoms
=
________
Chemistry An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition
Copyright © 2012 by Pearson Education, Inc.
Solution
5
Give the molar mass for each element (to the tenths place).
A. 1 mole of K atoms
=
39.1 g of K
B. 1 mole of Sn atoms
=
118.7 g of Sn
C. 1 mole of Ca atoms
=
40.0 g of Ca
Chemistry An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition
Copyright © 2012 by Pearson Education, Inc.
Guide to Calculating Molar Mass
6
Chemistry An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition
Copyright © 2012 by Pearson Education, Inc.
Molar Mass of the Compound C2H6O
7
To calculate the molar mass of C2H6O:
Step 1 Obtain the molar mass of each element.
1 mole of C = 12.0 g of C
1 mole of H = 1.01 g of H
1 mole of O = 16.0 g of O
Chemistry An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition
Copyright © 2012 by Pearson Education, Inc.
Molar Mass of the Compound C2H6O
8
Step 2 Multiply each molar mass by the number of moles
(subscripts) in the formula.
2 moles C x 12.0 g C
= 24.0 g of C
1 mole C
6 moles H x 1.01 g H
= 6.06 g of H
1 mole H
1 mole O x 16.0 g O
= 16.0 g of O
1 mole O
Chemistry An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition
Copyright © 2012 by Pearson Education, Inc.
Molar Mass of the Compound C2H6O
9
Step 3 Calculate the molar mass by adding the masses of
the elements.
2 moles of C
= 24.0 g of C
6 moles of H
=
6.06 g of H
1 mole of O
= 16.0 g of O
Molar mass of C2H6O
= 46.1 g of C2H6O
Chemistry An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition
Copyright © 2012 by Pearson Education, Inc.
One-Mole Quantities
10
Chemistry An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition
Copyright © 2012 by Pearson Education, Inc.
Learning Check
11
What is the molar mass of each compound?
A. K2O
B. Al(OH)3
Chemistry An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition
Copyright © 2012 by Pearson Education, Inc.
Solution
12
What is the molar mass of each compound?
Step 1 Obtain the molar mass of each element.
A. K2O
K
= 39.1 g/mole
O
= 16.0 g/mole
B. Al(OH)3 Al
O
H
= 27.0 g/mole
= 16.0 g/mole
= 1.01 g/mole
Chemistry An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition
Copyright © 2012 by Pearson Education, Inc.
Solution
13
What is the molar mass of each compound?
Step 2 Multiply each molar mass by the number of moles
(subscripts) in the formula.
A. K2O
2 moles K x 39.1 g K = 78.2 g of K
1 mole K
1 mole O x 16.0 g O = 16.0 g of O
1 mole O
Chemistry An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition
Copyright © 2012 by Pearson Education, Inc.
Solution
14
What is the molar mass of each compound?
Step 2 Multiply each molar mass by the number of moles
(subscripts) in the formula.
B. Al(OH)3
1 mole Al x 27.0 g Al
= 27.0 g of Al
1 mole Al
3 moles O x 16.0 g O
= 48.0 g of O
1 mole O
3 moles H x 1.01 g H
= 3.03 g of H
1 mole H
Chemistry An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition
Copyright © 2012 by Pearson Education, Inc.
Solution
15
What is the molar mass of each compound?
Step 3 Calculate the molar mass by adding the masses of
the elements.
A. K2O
2 moles of K = 78.2 g of C
1 mole of O = 16.0 g of O
Molar mass of K2O = 94.2 g of K2O
B. Al(OH)3
1 mole of Al = 27.0 g of Al
3 moles of O = 48.0 g of O
3 moles of H = 3.03 g of H
Molar mass of Al(OH)3 = 78.0 g of Al(OH)3
Chemistry An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition
Copyright © 2012 by Pearson Education, Inc.
Learning Check
16
Prozac, C17H18F3NO, is an antidepressant that inhibits the
uptake of serotonin by the brain. What is the molar mass
of Prozac?
A. 40.1 g/mole
B. 262 g/mole
C. 309 g/mole
Chemistry An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition
Copyright © 2012 by Pearson Education, Inc.
Solution
17
Step 1 Obtain the molar mass of each element.
1 mole of C
= 12.0 g of C
1 mole of H
= 1.01 g of H
1 mole of F
1 mole of N
1 mole of O
= 19.0 g of F
= 14.0 g of N
= 16.0 g of O
Chemistry An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition
Copyright © 2012 by Pearson Education, Inc.
Solution
18
Step 2 Multiply each molar mass by the number of moles
(subscripts) in the formula.
17 moles C x 12.0 g
= 204 g of C
1 mole C
18 moles H x 1.01 g
= 18.2 g of H
1 mole H
3 moles F x 19.0 g
= 57.0 g of F
1 mole F
1 mole N x 14.0 g
= 14.0 g of N
1 mole N
1 mole O x 16.0 g
= 16.0 g of O
1 mole O
Chemistry An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition
Copyright © 2012 by Pearson Education, Inc.
Solution
19
Step 3 Calculate the molar mass by adding the masses of
the elements:
1 mole of C17H18F3NO = 309 g of C17H18F3NO
Chemistry An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition
Copyright © 2012 by Pearson Education, Inc.
Calculations Using Molar Mass
20
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, is
1 mole of CH4 = 16.0 g of CH4 (molar mass equality)
Conversion factors:
16.0 g CH4
and
1 mole CH4
1 mole CH4
16.0 g CH4
Chemistry An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition
Copyright © 2012 by Pearson Education, Inc.
Guide to Calculating Moles from Mass
21
Chemistry An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition
Copyright © 2012 by Pearson Education, Inc.
Converting Mass to Moles of
Compound NaCl
22
A box of table salt, NaCl, contains 737 g of NaCl.
How many moles of NaCl are in the box?
Chemistry An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition
Copyright © 2012 by Pearson Education, Inc.
Converting Mass to Moles of
Compound NaCl
23
A box of table salt, NaCl, contains 737 g of NaCl.
How many moles of NaCl are in the box?
Step 1 State the given and needed quantities.
Given:
737 g of NaCl
Need:
moles of NaCl
Step 2 Write a plan to convert grams to moles.
molar mass
Grams of NaCl
Moles of NaCl
Chemistry An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition
Copyright © 2012 by Pearson Education, Inc.
Converting Mass to Moles of
Compound NaCl
24
Step 3 Determine the molar mass and write conversion factors.
Molar Mass
1 mole Na x 23.0 g Na
= 23.0 g of Na
1 mole Na
1 mole Cl x 35.5 g Cl
= 35.5 g of Cl
1 mole Cl
58.5 g of NaCl
Conversion Factors
1 mole of NaCl = 58.5 g of NaCl
58.5 g NaCl and 1 mole NaCl
1 mole NaCl
58.5 g NaCl
Chemistry An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition
Copyright © 2012 by Pearson Education, Inc.
Converting Mass to Moles of
Compound NaCl
25
Step 4 Set up the problem to convert grams to moles.
737 g NaCl x 1 mole NaCl = 12.6 moles of NaCl
58.5 g NaCl
Chemistry An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition
Copyright © 2012 by Pearson Education, Inc.
Map: Mass – Moles – Particles
26
Chemistry An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition
Copyright © 2012 by Pearson Education, Inc.
Learning Check
27
Allyl sulfide, C6H10S, is a compound that has
the odor of garlic. How many moles of
C6H10S are in 225 g?
Chemistry An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition
Copyright © 2012 by Pearson Education, Inc.
Solution
28
Step 1 State the given and needed quantities.
Given:
225 g of C6H10S
Need:
moles of C6H10S
Step 2 Write a plan to convert grams to moles.
molar mass
Grams of C6H10S
Moles of C6H10S
Chemistry An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition
Copyright © 2012 by Pearson Education, Inc.
Solution
29
Step 3 Determine the molar mass and write conversion factors.
Molar mass
6 moles C x 12.0 g C
= 76.0 g of C
1 mole C
10 moles H x 1.01 g H = 10.1 g of H
1 mole H
1 mole S x 32.1 g S
= 32.1 g of S
1 mole S
= 114.2 g of C6H10S
Chemistry An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition
Copyright © 2012 by Pearson Education, Inc.
Solution
30
Step 3 Determine the molar mass and write conversion factors.
Conversion Factors
1 mole of C6H10S = 114.2 g of C6H10S
114.2 g C6H10S and 1 mole C6H10S
1 mole C6H10S
114.2 g C6H10S
Step 4 Set up the problem to convert grams to moles.
225 g C6H10S x 1 mole C6H10S
114.2 g C6H10S
= 19.7 moles of C6H10S
Chemistry An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition
Copyright © 2012 by Pearson Education, Inc.