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

Chapter 5 Chemical Quantities and Reactions 5.2 Molar Mass

Molar Mass The molar mass is the mass of 1 mole of an element is the atomic mass expressed in grams

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 of Ag = 12.0 g of C = 32.1 g of S

Learning Check 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 = ________

Solution 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

Guide to Calculating Molar Mass

Molar Mass of the Compound C2H6O 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

Molar Mass of the Compound C2H6O 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

Molar Mass of the Compound C2H6O 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

One-Mole Quantities

Learning Check What is the molar mass of each compound? A. K2O B. Al(OH)3

Solution 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 = 27.0 g/mole O = 16.0 g/mole H = 1.01 g/mole

Solution 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

Solution 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

Solution 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

Learning Check 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

Solution 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 = 19.0 g of F 1 mole of N = 14.0 g of N 1 mole of O = 16.0 g of O

Solution 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

Solution Step 3 Calculate the molar mass by adding the masses of the elements: 1 mole of C17H18F3NO = 309 g of C17H18F3NO

Calculations Using Molar Mass 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

Guide to Calculating Moles from Mass

Converting Mass to Moles of Compound NaCl A box of table salt, NaCl, contains 737 g of NaCl. How many moles of NaCl are in the box?

Converting Mass to Moles of Compound NaCl 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

Converting Mass to Moles of Compound NaCl 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

Converting Mass to Moles of Compound NaCl 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

Map: Mass – Moles – Particles

Learning Check Allyl sulfide, C6H10S, is a compound that has the odor of garlic. How many moles of C6H10S are in 225 g?

Solution 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

Solution Step 3 Determine the molar mass and write conversion factors. 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

Solution Step 3 Determine the molar mass and write 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