Fund. E & F - Mole, Empiricals & Molecular Formulas

Fund. E & F - Mole, Empiricals & Molecular...

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Fundamentals E & F: Moles, Mass Percents, Empirical and Molecular Formulas Atomic Mass: How much does one atom weight? 1 amu = 1.66 x 10 -24 g atomic mass of an element is the average atomic mass for all the isotopes in the ratio that those isotopes occur so sample can be treated as though each C atoms weighs 12.01 amu 3000 atoms x 14.01 amu/atom = 42,030 amu (42.01 x 10 3 amu = 4.201 x 10 4 amu) (4.201 x 10 4 ) x (1.66 x 10 -24 g)/1 amu = 6.97366 x 10 -20 g Number of sodium atoms in 8.56 x 10 19 amu (average atomic mass of sodium 22.99 amu) 8.56 x 10 19 amu x 1 sodium atom/22.99 amu = 3.73 x 10 18 sodium atoms The Mole: Allow us to count mass # of atoms when the weight is given in grams (with out using such small units!) One mole = 6.022 x 10 23 units (Avogadro’s number) A dozen eggs contains 12 eggs A mole of eggs contains 6.022 x 10 23 eggs A mole of nitrogen contains 6.022 x 10 23 nitrogen atoms Any element that weights a number of grams equal to the average atomic mass of that element contains 1 mole or 6.022 x 10 23 atoms 12.01 g of carbon contain 1 mole or 6.022 x 10 23 carbon atoms 26.98 g of aluminum contain 1 mole or 6.022 x 10 23 aluminum atoms **To have the same number of atoms in my samples I would need 12.01 g of carbon and 26.98 g of aluminum I have 24.56 g of sodium (22.99 amu) - how many moles? how many atoms? How much does 1 mole weigh?
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Fund. E & F - Mole, Empiricals & Molecular...

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