chapter 3

# chapter 3 - Chapter 3 3.1 Stoichiometry quantities of...

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Chapter 3 3.1 S 3.1 S toichiometry toichiometry quantities quantities of substances consumed and of substances consumed and produced in chemical processes. produced in chemical processes.

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REACTANT(S ) PRODUCT(S) AMOUNTS TYPE OF REACTION, PATHWAY SPEED OF REACTION ENERGY CHANGES IN A REACTION

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3.2 ATOMIC MASSES Every atom has its own unique atomic mass based on a standard comparison or relative scale The relative atomic mass scale is now based on an isotope of carbon, 12 C , which is given the exact value of 12 amu (* atomic mass unit ).
Mass spectrometer gives very accurate values of relative masses Isotopes and abundances What are isotopes? 12 C(12 amu), 13 C(13.003355 amu) and 14 C 98.89% 1.11%, ~ 0% Weighted average is called atomic mass/weight

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mass number Mass (amu) percent abundance 12 12(exact) 98.89 13 13.003355 1.11 Example #1: Carbon 12 amu × 98.89 % + 13.003355 ×1.11% = 11.8668 amu + 0.14434 amu = 12.01amu Average atomic mass of C:
Example #2: Nitrogen mass number Mass (amu) percent abundance 14 14.003074 99.63 15 15.000108 0.37 Average atomic mass of N: finish the calculation ! The answer is 14.01 amu

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1 mole (mol) is the amount of a substance that contains as many entities as there are in exactly 12 grams of 12 C. Avogadro’s number: 6.02214 x 10 23 One mole of ( ) contains 6.022 x 10 23 units of ( ). 3.3 The Mole
3.3 The Mole 1 mole of 12 C = 6.022 x 10 23 atoms of 12 C = exact 12 g of 12 C = atomic mass of 12 C in grams. The atomic mass for Au is 197.0 amu I mole of Au is 197.0 g The atomic mass of sulfur is 32.07 amu 32.07 g sulfur is I mole of sulfur The atomic mass of copper is 63.55 amu I mole copper (6.022 x 10 23 ) atoms is 63.55 g The mass of 1 mole of an element is equal to its atomic mass in grams.

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1 mole of copper = ____________ atoms of copper = _______________g of copper 1 mole iodine = _____________ atoms of iodine= ____________g of iodine 6.022 x 10 23 amu = 1 gram Exact number
Calculations How many atoms of Na are present in 3.45 moles of Na How many moles are present in 4.05 x 10 23 atoms of aluminum? 3.45 mol Na × 6.022×10 23 atoms/mol = 4.05 x 10 23 Al atoms × 6.022×10 23 atoms 1 mol =

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3.4 Molar Mass What the mass of 1 mole of methane (CH 4 )? Mass of 1 mol C = 12.01 g Mass of 4 mol H = 4 × 1.008 g Mass of 1 mol CH 4 = 16.04 g The molar mass of a substance is the mass in grams of one mole of the substance. e.g. 1 mol Acetic acid CH 3 COOH 1 mole acetic acid contains 2 mol C, 4 mol H and 2 mol O 2×12.01g 4×1.008g 2×16.00g 60.05 g e.g. 1 mol table salt NaCl 1 mole sodium chloride contains 1mol Na and 1 mol Cl 1×22.99 g 1×35.45 g 58.44 g
What is the molar mass of the following compounds? A. Iron(III) chloride

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## This note was uploaded on 11/27/2011 for the course CHEM 101 taught by Professor Luikang during the Spring '10 term at SPSU.

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chapter 3 - Chapter 3 3.1 Stoichiometry quantities of...

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