Chapter 5 Chemical Quantities and Reactions 5.1 The Mole

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

Avogadro's Number Small particles such as atoms, molecules, and ions are counted using the mole. 1 mole = 6.02 x 1023 items Avogadro’s number 602 000 000 000 000 000 000 000 = 6.02 x 1023

Mole of Atoms 1 mole of an element = 6.02 x 1023 atoms of that element 1 mole of carbon = 6.02 x 1023 atoms of carbon 1 mole of sodium = 6.02 x 1023 atoms of sodium

Number of Particles in One-Mole Samples

Avogadro's Number Avogadro’s number, 6.02 x 1023, can be written as an equality and as two conversion factors. Equality: 1 mole = 6.02 x 1023 particles Conversion Factors: 6.02 x 1023 particles and 1 mole 1 mole 6.02 x 1023 particles

Guide to Calculating Atoms or Molecules

Converting Moles to Particles Avogadro’s number is used to convert moles of a substance to particles. How many CO2 molecules are in 0.50 mole of CO2? Step 1 State the needed and given quantities: Given: 0.50 mole of CO2 Needed: molecules of CO2

Converting Moles to Particles Step 2 Write a plan to convert moles to atoms or molecules: Avogadro’s number moles of CO2 molecules of CO2 Step 3 Use Avogadro’s number to write conversion factors. 1 mole of CO2 = 6.02 x 1023 molecules of CO2 6.02 x 1023 CO2 molecules and 1 mole CO2  1 mole CO2 6.02 x 1023 CO2 molecules

Converting Moles to Particles Step 4 Set up the problem to calculate the number of particles. 0.50 mole CO2 x 6.02 x 1023 molecules CO2 1 mole CO2 = 3.01 x 1023 molecules of CO2

Learning Check The number of atoms in 2.0 mole of Al atoms is: A. 2.0 Al atoms B. 3.0 x 1023 Al atoms C. 1.2 x 1024 Al atoms

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

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 1023 atoms of Al 6.02 x 1023 atoms Al and 1 mole A 1 mole Al 6.02 x 1023 atoms Al

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 1023 Al atoms 1 mole Al = 1.2 x 1024 Al atoms

Learning Check The number of moles of S in 1.8 x 1024 atoms of S is: A. 1.0 mole of S atoms B. 3.0 moles of S atoms C. 1.1 x 1048 moles of S atoms

Solution The number of moles of S in 1.8 x 1024 atoms of S is: Step 1 State the needed and given quantities: Given: 1.8 x 1024 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

Solution The number of moles of S in 1.8 x 1024 atoms of S is: Step 3 Use Avogadro’s number to write conversion factors. 1 mole S = 6.02 x 1023 atoms of S 6.02 x 1023 atoms S and 1 mole S 1 mole S 6.02 x 1023 atoms S

Solution The number of moles of S in 1.8 x 1024 atoms of S is: Step 4 Set up the problem to calculate the number of particles. B. 1.8 x 1024 S atoms x 1 mole S 6.02 x 1023 S atoms = 3.0 moles of S atoms

Moles of Elements in a Formula

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 C9H8O4 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

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, C9H8O4, the possible conversion factors are: 9 moles C 8 moles H 4 moles O 1 mole C9H8O4 1 mole C9H8O4 1 mole C9H8O4 9 moles C 8 moles H 4 moles O

Learning Check How many atoms of O are in 0.150 mole of aspirin, C9H8O4?

Solution Step 1 State the needed and given quantities: Given: 0.150 mole of C9H8O4 Need: molecules of C9H8O4 Step 2 Write a plan to convert moles to atoms or molecules: Moles of aspirin Moles of O Atoms of O

Solution Step 3 Use Avogadro’s number to write conversion factors. Subscript factor: 1 mole of C9H8O4 = 4 moles of O 1 mole C9H8O4 and 4 moles O 4 moles O 1 mole C9H8O4 Avogadro’s number: 1 mole of O = 6.02 x 1023 atoms of O 1 mole O and 6.02 x 1023 atoms O 6.02 x 1023 atoms O 1 mole O

Solution Step 4 Set up the problem to calculate the number of particles. 0.150 mole C9H8O4 x 4 mole O x 6.02 x 1023 atoms O 1 mole C9H8O4 1 mole O = 3.61 x 1023 atoms of O