Chapter 6

# Chapter 6 - Chapter 6 Chemical composition 6.1 o How much...

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Chapter 6: Chemical composition 6.1 o How much sodium? Chemical composition is important not just for assessing dietary sodium, but for addressing many other issues as well including pollution 6.2 o Counting nails by the pound 6.3 o Counting atoms by the gram The chemist’s dozen is called the mole (mol). Mole (mol): also known as Avogadro’s number, it has a value of 6.022X10 23 . Its used for counting atoms. the first thing to understand about the mole is that it can specify Avogadro’s number of anything. The second thing to understand about the mole is how it gets its specific value. The numerical value of the mole is defined as being equal to the number of atoms in exactly 12 g of pure carbon-12. To convert between moles of atoms and number of atoms we simply use the conversion factors: . . 1 mol atoms6 022X1023atoms or 6 022X1023atoms1 mol atoms Converting between grams and moles of an element: We just learned how to convert between moles and number of atoms, we need one more conversion factor to convert from the mass of a sample to the number of atoms in the sample. For atoms, we need the mass of one mole of atoms Molar mass: the mass of 1 mol of atoms of an element. The value of an element’s molar mass in grams per mole is numerically equal to the elements atomic mass in atomic mass units. 12.01 g carbon = 1 mol carbon = 6.022X10 23 C atoms.

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The lighter the atom, the less mass in a mole of that atom. Therefore, the molar mass of any element becomes a conversion factor between grams of that element and moles of that element. . = . . 12 01g C 1 mol C or12 01 g C1 mol C or 1 mol C12 01 g C * . * . x g C1 1 mol C12 01 g C 6 022x1023 C atoms1 mol =# C of carbon atoms 6.4 o Counting molecules by the gram
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## This note was uploaded on 07/02/2008 for the course 004 007 taught by Professor Haverhals during the Summer '08 term at University of Iowa.

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Chapter 6 - Chapter 6 Chemical composition 6.1 o How much...

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