mole - The Mole Q: how long would it take to spend a mole...

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Unformatted text preview: The Mole Q: how long would it take to spend a mole of $1 coins if they were being spent at a rate of 1 billion per second? Background: atomic masses • Look at the “atomic masses” on the periodic table. What do these represent? • E.g. the atomic mass of C is 12 (atomic # is 6) • We know there are 6 protons and 6 neutrons • Protons and neutrons have roughly the same mass. So, C weighs 12 u (atomic mass units). • What is the actual mass of a C atom? • Answer: approx. 2 x 10-23 grams (protons and neutrons each weigh about 1.7 x10-24 grams) Two problems 1. Atomic masses do not convert easily to grams The Mole With these problems, why use atomic mass at all? 1. Masses give information about # of p + , n , e – 2. It is useful to know relative mass E.g. Q - What ratio is needed to make H 2 O? A - 2 : 1 by atoms, but 2 : 16 by mass • It is useful to associate atomic mass with a mass in grams. It has been found that 1 g H, 12 g C, or 23 g Na have 6.02 x 10 23 atoms • 6.02 x 10 23 is a “mole” or “Avogadro’s number” • “mol” is used in equations, “mole” is used in writing; one gram = 1 g, one mole = 1 mol....
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This note was uploaded on 11/09/2011 for the course CHEM 110 taught by Professor Sullivan during the Fall '10 term at BYU.

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mole - The Mole Q: how long would it take to spend a mole...

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