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MolesI pledge allegiance to the mole, and to the science from which it comes, one SI unit, extremely divisible, with micromoles and millimoles for all.    

(Provided by R. Thomas Myers - Kent State University, Kent, OH)

 

I pledge allegiance to the mole, to the International Union of Pure and Applied Chemistry, and to the atomic mass for which it stands, one number, most divisible, with atoms and molecules for all.   

(Provided by Sylvia Cooper - Morgantown High School, Morgantown, WV

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Avagadro’s Constant

1 mol = 6.02 x 10 23

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Here it is again: one mole of ANY specified entity contains 6.022 x 1023 of that entity.

For example: One mole of donuts contains 6.022 x 1023 donuts One mole of H2O contains 6.022 x 1023 molecules One mole of nails contains 6.022 x 1023 nails One mole of Fe contains 6.022 x 1023 atoms One mole of dogs contains 6.022 x 1023 dogs One mole of electrons contains 6.022 x 1023

electrons

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What is molar mass ?

The mass in grams of 1 mole of a substance

When we weigh one mole of a substance on a balance, this is called a "molar mass" and has the units g/mol (grams per mole). This idea is very critical because it is used all the time.

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Conversion factors

Give two conversion factors for the molar masses of the following

Na

Br2

Ba(OH)2

1 mol Na 22.99g Na

22.99g Na 1 mol

1 mol Br2 159.8g Br2

159.8g Br2 1 mol Br2

1 mol Ba(OH)2 171.3g Ba(OH)2

171.3g Ba(OH)2 1 mol Ba(OH)2

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Question ?

How many grams are in 2.5 mol of Na ?

2.5 mol Na x 22.99g Na = 1 mol Na

57.48 g Na

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Question ?

Convert 0.25 moles of Br2 to grams

.25 mol Br2 x 159.8 g Br 2

1 mol Br2

=39.95 g Br2

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Question ?

How many moles are in 125 g of Ba(OH)2 ?

125 g Ba(OH)2 x 1 mol Ba(OH)2

1 171 g Ba(OH)2

= .73 mol Ba(OH)2