Transcript Chapter 1
Chapter 7 Lecture Basic Chemistry Fourth Edition Chapter 7 Chemical Quantities 7.1 The Mole Learning Goal Use Avogadro's number to determine the number of particles in a mole. © 2014 Pearson Education, Inc. Chapter 7 Readiness Key Math Skills • Calculating a Percentage (1.4C) • Solving Equations (1.4D) • Using Scientific Notation (2.2) © 2014 Pearson Education, Inc. Chapter 7 Readiness Core Chemistry Skills • Counting Significant Figures (2.3) • Using Significant Figures in Calculations (2.4) • Writing Conversion Factors from Equalities (2.6) • Using Conversion Factors (2.7) © 2014 Pearson Education, Inc. The Mole Counting Units • 1 dozen = 12 • 1 case = 24 cans • Avogadro’s number = 6.022 × 1023 Atoms are so small it takes a large number of them to weigh and use in a chemical reaction. © 2014 Pearson Education, Inc. Avogadro’s Number A mole (mol) is a unit that represents the same number of particles as there are carbon atoms in 12.01 g of carbon. One mole of any element contains 6.022 × 1023 atoms of that element. 1 mol of Element Number of Atoms 1 mol C = 6.022 × 1023 C atoms 1 mol Au = 6.022 × 1023 Au atoms © 2014 Pearson Education, Inc. Avogadro’s Number One mole of • an element contains 6.022 × 1023 atoms • a molecule contains 6.022 × 1023 molecules • an ion contains 6.022 × 1023 ions • a formula unit contains 6.022 × 1023 formula units © 2014 Pearson Education, Inc. Number of Particles in One Mole © 2014 Pearson Education, Inc. Avogadro’s number as a Conversion Factor Avogadro’s number (6.022 × 1023) can be written as an equality and two conversion factors. Equality: 1 mole = 6.022 × 1023 particles Conversion Factors: © 2014 Pearson Education, Inc. Using Avogadro’s Number Avogadro’s number converts moles of a substance to the number of atoms. How many Cu atoms are in 0.50 mol of Cu? © 2014 Pearson Education, Inc. Using Avogadro’s Number Avogadro’s number converts the number of molecules to moles of a molecule. How many moles of CO2 are in 2.50 × 1024 molecules of CO2? 2.50 × 1024 molecules CO2 = 4.15 mole CO2 © 2014 Pearson Education, Inc. Guide to Calculating the Atoms or Molecules of a Substance © 2014 Pearson Education, Inc. Learning Check The number of atoms in 2.0 moles of aluminum is A. 2.0 Al atoms B. 3.0 × 1023 Al atoms C. 1.2 × 1024 Al atoms © 2014 Pearson Education, Inc. Solution The number of atoms in 2.0 moles of aluminum is Step 1 State the given and needed quantities. Given = 2.0 moles Al Need = atoms of Al Step 2 Write a plan to convert moles to atoms. Moles Al © 2014 Pearson Education, Inc. Avogadro’s Number atoms Al Solution The number of atoms in 2.0 moles of aluminum is Step 3 Use Avogadro’s number to write conversion factors. Equality: 1 mole Al = 6.022 × 1023 atoms Al © 2014 Pearson Education, Inc. Solution The number of atoms in 2.0 moles of aluminum is Step 4 Set up the problem to calculate the number of particles = 1.2 × 1024 atoms Al Answer C is correct. © 2014 Pearson Education, Inc. Moles of Element in a Chemical Formula The subscripts in a formula state • the relationship of atoms in the formula • the moles of each element in one mole of compound NH3 1 molecule 1 mole NH3 © 2014 Pearson Education, Inc. 1 atom N 1 mole N 3 atoms H 3 moles H Chemical Formulas, Subscripts Aspirin, C9H8O4, is used to reduce pain and inflammation. © 2014 Pearson Education, Inc. Chemical Formulas, Subscripts The subscripts in the chemical formula for aspirin, C9H8O4, express the ratio of atoms or moles. © 2014 Pearson Education, Inc. Chemical Formulas, Conversion Factors The subscripts from the formula, C9H8O4, can be used in conversion factors. © 2014 Pearson Education, Inc. Guide to Calculating Moles © 2014 Pearson Education, Inc. Learning Check How many moles of carbon are present in 2.50 moles of aspirin, C9H8O4? © 2014 Pearson Education, Inc. Solution How many moles of oxygen are present in 2.50 moles of aspirin, C9H8O4? Step 1 State the given and needed quantities. Given: 2.50 moles aspirin, C9H8O4 Need: moles of O Step 2 Write a plan to connect moles of a compound to moles of an element. moles C9H8O4 © 2014 Pearson Education, Inc. Subscript moles O Solution How many moles of oxygen are present in 2.50 moles of aspirin, C9H8O4? Step 3 Write equalities and conversion factors. 1 mole C9H8O4 = 4 moles O © 2014 Pearson Education, Inc. Solution How many moles of oxygen are present in 2.50 moles of aspirin, C9H8O4? Step 4 Set up the problem to calculate the moles of an element. © 2014 Pearson Education, Inc. Learning Check The number of moles of sulfur (S) in 1.8 × 1024 atoms of sulfur is _____. A. 1.0 mol of S atoms B. 3.0 mol of S atoms C. 1.1 × 1048 mol of S atoms © 2014 Pearson Education, Inc. Solution The number of moles of sulfur (S) in 1.8 × 1024 atoms of sulfur is _____. Step 1 State the given and needed quantities. Given: 1.8 × 1024 atoms of S Need: moles of S Step 2 Write a plan to connect moles to atoms or molecules. atoms S © 2014 Pearson Education, Inc. Avogadro's number moles S Solution The number of moles of sulfur (S) in 1.8 × 1024 atoms of sulfur is _____. Step 3 Use Avogadro’s number to write conversion factors. 1 mole S = 6.022 × 1023 atoms © 2014 Pearson Education, Inc. Solution The number of moles of sulfur (S) in 1.8 × 1024 atoms of sulfur is _____. Step 4 Set up the problem to calculate the number of particles. The correct answer is B. © 2014 Pearson Education, Inc.