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Tro's Introductory Chemistry, Chapter 6 1 2.3 Counting Atoms or Molecules by Moles The number of atoms or molecules we will use is 6.022 x 10 23 and we call this a mole 1 mole = 6.022 x 10 23 particles Like 1 dozen = 12 particles
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Tro's Introductory Chemistry, Chapter 62 The number of particles in 1 mole is called Avogadro’s Number = 6.0221421 x 10 23
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We can make two conversion factors: A) B) 1 mole 6.022 x 10 23 atoms 6.022 x 10 23 atoms 1 mole A)For converting atoms mole B)For converting mole atoms
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Practice 1 1. How many atoms are in 1 mole of aluminum? 2. How many molecules in 1 mole of sulfur dioxide? Conversion sequence: moles → atoms, molecules
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Tro's Introductory Chemistry, Chapter 65 Moles and Mass The mass of one mole of atoms or molecules is called the molar mass
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Tro's Introductory Chemistry, Chapter 6 6 Moles and Mass (cont.) The molar mass of an element, in grams, is numerically equal to the element’s atomic mass.
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1 mole is 6.022 x 10 23 atoms and has a mass of exactly 12 grams
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Tro's Introductory Chemistry, Chapter 6 8 Mole and Mass Relationships 1 mole Sulfur 32.06 g 1 mole Carbon 12.01 g
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Tro's Introductory Chemistry, Chapter 6 9 Moles and Mass (cont.) The molar mass of a compound, in grams, is numerically equal to the sum of the atomic masses of the elements in the compounds formula.
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Tro's Introductory Chemistry, Chapter 610 The molar mass of water is calculated from the atomic weights of hydrogen and oxygen. Formula = H 2 O Formula Mass = 2(1.01 amu H) + 16.00 amu O = 18.02 amu Molar Mass = 18.02 g
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Practice 3 Calculate formula mass and Molar Mass FORMULAFORMULA MASS (amu) MOLES Br 2 1 Ni 1 BaCl 2 1 MOLAR MASS (g)
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Practice 4 How many moles for each of the following? 1.44 grams of CO 2 2. 55.85 g of iron Conversion sequence: grams → moles
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Tro's Introductory Chemistry, Chapter 613 1 spider 8 legs 1 chair 4 legs 1 H 2 O molecule 2 H atoms 1 O atom
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Tro's Introductory Chemistry, Chapter 614 Mole Relationships in Chemical Formulas Moles of CompoundMoles of Constituents 1 mol NaCl1 mole Na, 1 mole Cl 1 mol H 2 O2 mol H, 1 mole O 1 mol CaCO 3 1 mol Ca, 1 mol C, 3 mol O 1 mol C 6 H 12 O 6 6 mol C, 12 mol H, 6 mol O Aka…Mole Ratios… always whole number ratios
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Tro's Introductory Chemistry, Chapter 6 15 Moles, Particles and Masses Moles of Compound Moles of Constituents Number of particles Mass (g) 1 mol NaCl1 mole Na, 1 mole Cl 6.02 x 10 23 Na 1.20 x 10 24 Cl 22.99 g Na 70.90 g Cl 1 mol H 2 O2 mol H, 1 mole O 1.20 x 10 24 H 6.02 x 10 23 O 2.08 g H 16.00 g O
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