Chapter 6 Chemistry Notes

The problem is that at the macroscopic level the

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Unformatted text preview: e, i.e. the atoms that are connected with bonds. We cannot tell the molecular formula without additional info.! 5 9/23/2013 Finding the Molecular Formula Suppose the molecular mass was determined by mass spectroscopy to be 62.07 g/mol. From FDA study Gas Chromatography - Mass Spectrometry (GC-MS) Screening Procedure for the Presence of Diethylene Glycol and Ethylene Glycol in Toothpaste The empirical formula was CH3O which has a molar mass of 31.03 g/mol. If we divide the molecular mass by the empirical mass: 62.07 g/mol ÷ 31.03 g/mol = 2. Therefore the molecular formula is (CH3O)2 or better C2H6O2. Notice: this data does not provide any information about how the atoms are connected. Molecular Formula vs. Empirical Formula Molecular Formula: C2H4O2 Acetic acid (vinegar). C Specific # atoms in compound Empirical Formula: CH2O Smallest whole-number ratios Empirical formula for acetic acid also empirical formula for Formaldehyde and others... Formaldehyde CH2O Methyl formate C2H4O2 Glucose C6H12O6 Dimethyl carbonate C3H6O3 Threose C4H8O4 Notice that composition and connectivity together define chemistry; what it is and how it is put together. http://www.fda.gov/Food/ScienceResearch/LaboratoryMethods/DrugChemicalResiduesMethodology/ucm113209.htm Advice: Master the Mole Old exam questions The mole simplifies many calculations linking macroscopic to molecular, and therefore has a very significant role in much of chemistry. Although at first it may seem to be non-intuitive, it is worth the effort to work through any initial confusion until you can use it with easy. By the time you finish studying CH. 6 and working the homework, be sure that you master the “Chemical Skills” that are summarized at the end of the chapter pp. 188-194 ( or pp.184-188 in 3rd ed.) Tools to be Mastered in Chapter 6 Mole = 6.022 x 1023 objects Atomic Mass ⇔ Molar Mass (amu=g/mol) or (6.022 x 1023 amu = 1 g) Master Moles to Master Chemistry! Conversion of Mass ⇔ Moles ⇔ # of things Chemical Formulas ⇔ Counting Conversions Chemical Formulas ⇔ Mass...
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This note was uploaded on 02/04/2014 for the course CHEM 004:007 taught by Professor Russellarsen during the Fall '13 term at University of Iowa.

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