Glencoe: Chapter 11 Sections 11.1 & 11.2 The Mole, part I Glencoe: Chapter 11 Sections 11.1 & 11.2
What is a mole?
What is a mole? A mole is a unit for counting very small particles. It is the SI base unit for measuring substances. Abbreviation: mol Particles include: molecules, formula units, ions and atoms.
In order to count such small particles, a mole has to be a large number. The value of the mole is: 6.02 * 1023 or 602,000,000,000,000,000,000,000 This number is called Avogadro’s number, after Count Amedeo Avogadro, who is credited with its discovery.
Mole-Particle & Particle-Mole Conversions To convert from moles to particles, multiply by Avogadro’s number. 1.5 mol X 6.02*1023 atoms 1 mol To convert from particles to moles, divide by Avogadro’s number. 1.2 * 1024 atoms X 1 mol 6.02*1023 atoms
Molar Mass The mass in grams of one mole of any substance is its molar mass. The molar mass of any element is its atomic mass from the periodic table. The molar mass of any compound is the sum of the molar masses of its component elements.
Examples The molar mass of sulfur is 32.06 g/mol. The molar mass of carbon is 12.01 g/mol. The molar mass of sodium chloride is 58.5 g/mol. The molar mass of water is 18.02 g/mol.
Mole-Mass & Mass-Mole Conversions To convert from moles to mass, multiply by the molar mass: 2 mol K X 39.09 g/mol = 78.18 g K To convert from mass to moles, divide by the molar mass: 36.04 g H2O / 18.02 g/mol = 2 mol H2O
Mass-Particle & Particle-Mass Conversions These problems requires two steps. To convert from mass to particles, divide by the molar mass, then multiply by Avogadro’s number: 25.0 g Au / 196.97 g/mol = .127 mol Au .127 mol Au X 6.02 * 1023 atoms = 7.65 * 1022 Au atoms
To convert from particles to mass, divide by Avogadro’s number, then multiply by the molar mass: 5.50 * 1022 He atoms / 6.02 * 1023 = .0914 mol He .0914 mol He X 4.00 g = .366 g He
Percent Composition In analytical chemistry, it is important to identify the elements in a compound, and determine their percent by mass. The percent by mass of each element in a compound is called percent composition. mass of element X 100 mass of compound
Complete Handout Problems To be continued… Complete Handout Problems