General Chemistry Chapter 2 September 14

General Chemistry Chapter 2 September 14 - iii. Molecular...

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September 14, 2009 Raebony General Chemistry : Chapter 3 I) The Mole a. One mole = number of things in 12 g of 12 C b. 6.022 x 10 23 II) Molar Mass (a.k.a. molar weight) a. Molar mass of an element is the mass of one mole of the element b. Molar mass of a molecular compound is the mass of 1 mole of molecules of that compound c. Molar mass of an ionic compound is the mass of one mole of formula units of that compound d. Finding the number of moles i. n = mass of substance / molar mass of substance = number of moles III)Mass Percentage and Empirical Formula a. Empirical formula is the simplest ratio of elements of moles in a compound i. From masses of mass % we can get empirical formula 1. from mass or mass % find moles From moles find ratio ii. Empirical formula tells us ONLY the ratio not the whole compound
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Unformatted text preview: iii. Molecular formula will be a multiple of the empirical formula. Therefore, the molar mass will be a multiple of the empirical mass 1. Example 2. C3H4O3 is the empirical formula of vitamin c a. Empirical mass = 88.06 g/ mol b. Molar Mass = 176.14 g c. 176.14/88.06 = 2 d. (C 3 H 4 O 3 )2 = C 6 H 8 O 6 b. Molecular formula is the actual numbers of atoms in a molecular compound c. Mass percentage is another way to express the ratio IV)Combustion Analysis a. Masses used from empirical formula come from combustion analysis b. Mainly used for organic compounds i. Study how much CO 2 , H 2 0, N 2 is released in the exhaust ii. Will mainly ignore N2 iii. Find the moles of Carbon and Hydrogen and Oxygen iv. Divide by the smallest number of moles found k...
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General Chemistry Chapter 2 September 14 - iii. Molecular...

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