# C3F2009 - Chapter 3. Stoichiometry of Formulas and...

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© Prof. Geanangel, CHEM 1331 Chapter 3 Department of Chemistry, University of Houston 1 Chapter 3. Stoichiometry of Formulas and Equations 3.5 Fundamentals of Solution Stoichiometry 3.1 The Mole 3.2 Determining the Formula of Unknown Compounds 3.3 Writing and Balancing Chemical Equations 3.4 Calculating Amounts of Reactant and Product © Prof. Geanangel, CHEM 1331 Chapter 3 Department of Chemistry, University of Houston 2 A mole (mol) represents a fixed number of objects. One mol of a substance contains the same number of entities as there are atoms in 12 g of carbon-12. How many atoms are present in 12 g of carbon-12? Mole Quantities

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© Prof. Geanangel, CHEM 1331 Chapter 3 Department of Chemistry, University of Houston 3 One mol of H 2 O contains 6.02 x 10 23 H 2 O molecules; about 18 mL! 1 mol of anything contains 6.022 x 10 23 entities (Avogadro’s number) One mol of NaCl contains 6.02 x 10 23 NaCl formulas; 58 g, roughly 1 Tbsp © Prof. Geanangel, CHEM 1331 Chapter 3 Department of Chemistry, University of Houston 4 Use mole quantity to count formulas by weighing them. How does it work? Mass of 1 mol of particles = mass of 1 particle x 6.02 x 10 23 particles Note: mass of 1 atom in amu is numerically equal to the mass in g of 1 mole of atoms of the element. Mass of 1 H atom: 1.008 amu/H x 1.661x10 -24 g/amu = 1.674 x10 -24 g/H Mass of 1 mol of H atoms: 1.674 x10 -24 g/H atom x 6.022x10 23 H atoms = 1.008g One atom of sulfur has a mass of 32.07 amu; What is the mass of one mole of S atoms?
© Prof. Geanangel, CHEM 1331 Chapter 3 Department of Chemistry, University of Houston 5 To obtain one mole of zinc (6.02 x 10 23 atoms), weigh out 65.39 g zinc. Zn + S => ZnS © Prof. Geanangel, CHEM 1331 Chapter 3 Department of Chemistry, University of Houston 6 The molar mass (M) of a substance is the mass of one mole of atoms, molecules, or formula units. Molar mass has units of g/mol. Table 3.1 is a summary of mass terms and units Skill: Mass - Mole Conversions Use the molar mass of an element or compound to convert a given number of moles to mass : Mass ( g ) = no . moles x no . grams 1 mole

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Department of Chemistry, University of Houston 7 Use 1/M to convert any given mass in grams to the number of moles: Use Avogadro’s number to convert moles of substance to number of entities : No . mol = mass ( g ) x 1 mol no . grams No. of entities = no. moles x 6.02x10 23 1 mole No. of moles = no. entities x 1 mole 6.02x10 23 © Prof. Geanangel, CHEM 1331 Chapter 3 Department of Chemistry, University of Houston 8 Problem: Manganese is essential to bone growth. In 1.00 kg of bone was found 2.94 x10 -2 g Mn. How many Mn atoms were present in the bone sample? Plan:
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## This note was uploaded on 08/16/2011 for the course BIOL 1361-1362 taught by Professor Any during the Spring '08 term at University of Houston.

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C3F2009 - Chapter 3. Stoichiometry of Formulas and...

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