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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.

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Presentation on theme: "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."— Presentation transcript:

1 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

2 Tro's Introductory Chemistry, Chapter 62 The number of particles in 1 mole is called Avogadro’s Number = 6.0221421 x 10 23

3 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

4 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

5 Tro's Introductory Chemistry, Chapter 65 Moles and Mass The mass of one mole of atoms or molecules is called the molar mass

6 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.

7 1 mole is 6.022 x 10 23 atoms and has a mass of exactly 12 grams

8 Tro's Introductory Chemistry, Chapter 6 8 Mole and Mass Relationships 1 mole Sulfur 32.06 g 1 mole Carbon 12.01 g

9 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.

10 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

11 Practice 3 Calculate formula mass and Molar Mass FORMULAFORMULA MASS (amu) MOLES Br 2 1 Ni 1 BaCl 2 1 MOLAR MASS (g)

12 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

13 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

14 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

15 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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