Chapter 6 Chemistry Notes

97 the mole a mass to molecule converter we can also

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Unformatted text preview: m mol # Ethylene glycol (EG) C2H6O2 Called molar mass (MM) # atoms gram Application of Conversion relating to the use of Moles mol mol # atoms From last time: 1 mol 6.02x1023 = 2.01x10 23 Au atoms 65.3 g 196.9g 1 mol 1 mol 196.9g 2.01x1023 Au atoms = 65.3 g 6.02x1023 1 mol 2 coins=65.3g One More Tool- Counting Conversions The chemical formula together with mass/mole conversions can enable transformations between masses of different substances Example: What is the mass of oxygen in 1 lb (465 g) of ethylene glycol (EG)? FM=62.1 amu = 62.1 g/mol From the chemical formula C2H6O2 or structure There are two O-atoms per EG molecule: 2 O − atoms or 2 mol O 1 EG 1 mol EG FM=2*12.01+6*1.01+2*16.0=62.1 amu = 62.1 g/mol Mass EG 1 mol 6.02x1023 EGs 465 g 62.1g 1 mol = 4.51x1024 EG − molecules 1 mol EG 465 g EG 62.1 g EG mass Today’s Strategy: one molecule several skills/tools. Mol EG Mol O Use moles for counting conversions! Mass O 2 mol O 16 g O = 240. g oxygen 1 mol EG 1 mol O counting counting mass counting mass counting mass 4 9/23/2013 Old exam question The preceding result could also be obtained from the law of constant composition: Fall 2003, 39% difficulty How many oxygen atoms are contained in 2.0 mole of dioxygen (O2 )? X gO 16.0 amu − O = 465 g EG 62.1 amu − EG A. 16.0 amu − O X gO= 465 g EG = 120 g Oxygen 62.1 amu − EG B. C. D. E. 4 1.5 x 1023 3.0 x 1023 1.2 x 1024 2.4 x 1024 2 mol O - atoms 6.02x1023 O - atoms = ______ O - atoms 2.0 mol O 2 1 mol O 2 1 mol O - atoms NOTICE: You need to start including extended units. Moles of what, atoms of what, grams of what, etc. FW=62.1 g/mol Counting Conversions (continued) (aka stoichiometry) Example: What is the mass of C & H in 1 lb (465 g) of ethylene glycol (EG)? From the chemical formula C2H6O2 2 C − atoms or 2 mol C 1 EG 1 mol EG Mass EG Mol EG 6 H − atoms or 6 mol H 1 EG 1 mol EG Mol ? What have we accomplished? 1 mol EG 465 g EG 62.1 g EG 2 mol C 12 g C = 180. g oxygen 1 mol EG 1 mol C 6 mol H 1.01 g H = 45. g hydrogen 1 mol EG 1 mol H Can the Process Be Reversed? %O=100-38.7-9.7=51.6% The...
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