Chemistry An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Chapter 5 Chemical Quantities and Reactions 5.1 The Mole 1

Chemistry An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Counting Units Counting units A counting term states a specific number of items. 1 dozen eggs = 12 eggs 1 case soda = 24 cans 1 ream = 500 sheets of paper 2

Chemistry An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Avogadro's Number Small particles such as atoms, molecules, and ions are counted using the mole. 1 mole = 6.02 x items Avogadro’s number = 6.02 x

Chemistry An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Mole of Atoms 1 mole of an element = 6.02 x atoms of that element 1 mole of carbon= 6.02 x atoms of carbon 1 mole of sodium= 6.02 x atoms of sodium 4

Chemistry An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Number of Particles in One-Mole Samples 5

Chemistry An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Avogadro's Number Avogadro’s number, 6.02 x 10 23, can be written as an equality and as two conversion factors. Equality: 1 mole = 6.02 x particles Conversion Factors: 6.02 x particles and 1 mole 1 mole 6.02 x particles 6

Chemistry An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Guide to Calculating Atoms or Molecules 7

Chemistry An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Converting Moles to Particles Avogadro’s number is used to convert moles of a substance to particles. How many CO 2 molecules are in 0.50 mole of CO 2 ? Step 1 State the needed and given quantities: Given: 0.50 mole of CO 2 Needed: molecules of CO 2 8

Chemistry An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Converting Moles to Particles Step 2 Write a plan to convert moles to atoms or molecules: Avogadro’s number moles of CO 2 molecules of CO 2 Step 3 Use Avogadro’s number to write conversion factors. 1 mole of CO 2 = 6.02 x molecules of CO x CO 2 molecules and 1 mole CO 2 1 mole CO x CO 2 molecules 9

Chemistry An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Converting Moles to Particles Step 4 Set up the problem to calculate the number of particles mole CO 2 x 6.02 x molecules CO 2 1 mole CO 2 = 3.01 x molecules of CO 2 10

Chemistry An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Learning Check The number of atoms in 2.0 mole of Al atoms is: A. 2.0 Al atoms B. 3.0 x Al atoms C. 1.2 x Al atoms 11

Chemistry An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Solution The number of atoms in 2.0 moles of Al atoms is: Step 1 State the needed and given quantities: Given: 2.0 mole Al Needed: atoms of Al Step 2 Write a plan to convert moles to atoms or molecules: Avogadro’s number Moles of Al Atoms of Al 12

Chemistry An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Solution The number of atoms in 2.0 moles of Al atoms is: Step 3 Use Avogadro’s number to write conversion factors. 1 mole of Al = 6.02 x atoms of Al 6.02 x atoms Al and 1 mole A 1 mole Al 6.02 x atoms Al 13

Chemistry An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Solution The number of atoms in 2.0 moles of Al atoms is: Step 4 Set up the problem to calculate the number of particles. C. 2.0 moles Al x 6.02 x Al atoms 1 mole Al = 1.2 x Al atoms 14

Chemistry An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Learning Check The number of moles of S in 1.8 x atoms of S is: A. 1.0 mole of S atoms B. 3.0 moles of S atoms C. 1.1 x moles of S atoms 15

Chemistry An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Solution The number of moles of S in 1.8 x atoms of S is: Step 1 State the needed and given quantities: Given: 1.8 x atoms of S Needed: moles of S Step 2 Write a plan to convert moles to atoms or molecules: Avogadro’s number Atoms of S Moles of S 16

Chemistry An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Solution The number of moles of S in 1.8 x atoms of S is: Step 3 Use Avogadro’s number to write conversion factors. 1 mole S = 6.02 x atoms of S 6.02 x atoms S and 1 mole S 1 mole S 6.02 x atoms S 17

Chemistry An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Solution The number of moles of S in 1.8 x atoms of S is: Step 4 Set up the problem to calculate the number of particles. B. 1.8 x S atoms x 1 mole S 6.02 x S atoms = 3.0 moles of S atoms 18

Chemistry An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Moles of Elements in a Formula 19

Chemistry An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Moles of Elements in a Formula The subscripts in a formula show: the relationship of atoms in the formula the moles of each element in 1 mole of compound Aspirin C 9 H 8 O 4 1 molecule: 9 atoms of C 8 atoms of H 4 atoms of O 1 mole: 9 moles of C 8 moles of H 4 moles of O 20

Chemistry An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Moles of Elements in a Formula Subscripts are used to write conversion factors for moles of each element in 1 mole of a compound. For aspirin, C 9 H 8 O 4, the possible conversion factors are: 9 moles C 8 moles H 4 moles O 1 mole C 9 H 8 O 4 1 mole C 9 H 8 O 4 1 mole C 9 H 8 O 4 9 moles C 8 moles H 4 moles O 21

Chemistry An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Learning Check How many atoms of O are in mole of aspirin, C 9 H 8 O 4 ? 22

Chemistry An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Solution Step 1 State the needed and given quantities: Given: mole of C 9 H 8 O 4 Need: molecules of C 9 H 8 O 4 Step 2 Write a plan to convert moles to atoms or molecules: Moles of aspirin Moles of O Atoms of O 23

Chemistry An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Solution Step 3 Use Avogadro’s number to write conversion factors. Subscript factor: 1 mole of C 9 H 8 O 4 = 4 moles of O 1 mole C 9 H 8 O 4 and 4 moles O 4 moles O 1 mole C 9 H 8 O 4 Avogadro’s number: 1 mole of O = 6.02 x atoms of O 1 mole O and 6.02 x atoms O 6.02 x atoms O 1 mole O 24

Chemistry An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Solution Step 4 Set up the problem to calculate the number of particles mole C 9 H 8 O 4 x 4 mole O x 6.02 x atoms O 1 mole C 9 H 8 O 4 1 mole O = 3.61 x atoms of O 25