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What is the mass in grams of one atom of a particular isotope? Consider 1 atom of C-12. The isotope notation is: 6 protons 6 neutrons 6 electrons X 1.67 x 10 -24 g/proton = X 1.67 x 10 -24 g/neutron = X 9.11 x 10 -27 g/electron = 1.002 x 10 -23 g 5.466 x 10 -26 g 2.010 x 10 -23 g/atom 12 C 6

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2.010 x 10 -23 g/atom is a very small amount. Scientists cannot measure small quantities like this in the lab. Scientists want (NEED!) to be able to work with a useable quantity such as 10 grams or 50 grams. Is there a convenient way to measure larger quantities of atoms?

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Why not use the average atomic mass that is already on the periodic table? It is already a relative mass, right? Why reinvent the wheel?

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But the atomic mass on the chart is in AMU, not grams! We do not have an AMU balance!

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Then lets convert the number on the periodic chart from AMU to grams!

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Lets review what we already know…….. We already know that 1 atom of C-12 has a mass of 2.010 x 10 -23 g. (This is also equal to 12 amu!) We also want the atomic mass of 12.0 amu to become 12.0 g. So, the problem becomes this…….. 2.010 x 10 -23 g/atom C-12 X ????? atoms = 12.0 g C-12

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This quantity is called a MOLE. ????? = 6.0 x 10 23 atoms

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A MOLE (mol) is just a word representing a quantity. What does dozen mean?Yep, it means 12. But 12 what? 12 steers 12 dinosaurs 12 flags

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Just like the word dozen can stand for 12 things, the mole stands for 6.02 x 10 23 things. Things, however, are limited to AtomsMoleculesIons

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You have finally arrived at the MOLE. You can now start applying this new knowledge in many different ways! Have Fun!

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Stuff to Do With the Mole What is the mass of 1 mole of Cu atoms? How many moles of Cu atoms are there in 75 g of Cu? How many atoms of Cu are present in 200 g of Cu? What is the mass of 1 mole of Cu(NO 3 ) 2 ? How many moles of Cu(NO 3 ) 2 are there in 150 g of Cu(NO 3 ) 2 ? More mole problems are available at the ChemTeam Web Site. Visit it now!

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This is easy! We just learned that 1 mole of an element is equal to the atomic mass listed on the periodic table. 1 mole of Cu atoms has a mass of 63.5 grams. What Is The Mass Of 1 Mole Of Cu Atoms? Menu Remember, 1 atom of Cu has a mass of 63.5 amu. 1 mole of Cu atoms has a mass of 63.5 grams!

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This is easy! We just learned that 1 mole of a compound is equal to the sum of the atomic masses of each element in the compound. 1 mole of Cu atoms has a mass of 63.5 grams. + 2 moles of N atoms have a mass of 28.0 grams. + 6 moles of O atoms have a mass of 96.0 grams. What Is The Mass Of 1 Mole Of Cu(NO 3 ) 2 ? Menu One mole of Cu(NO 3 ) 2 has a mass of 187.5 g/mole.

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How many moles of Cu atoms are there in 75 g of Cu? Molar mass Cu = 63.5 g/mol Use this as a proportion! X = 1.18 mol Menu If we know that… 63.5 gCu 1 mole = thenwe also know that… 75 g Cu x mole Another way to set this up…. 75 g Cu x 1 mole Cu = 1.18 mol 63.5 g Cu

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How many moles of Cu(NO 3 ) 2 are there in 150 g of Cu(NO 3 ) 2 ? Molar mass Cu(NO 3 ) 2 = 187.5 g/mol Use this as a proportion! X = 0.8 mol Menu If we know that… 187.5 g Cu(NO 3 ) 2 1 mole = thenwe also know that… 150 g Cu(NO 3 ) 2 x mole Another way to set this up…. 150 g Cu(NO 3 ) 2 x 1 mole Cu(NO 3 ) 2 = 0.8 mol 187.5 g Cu(NO 3 ) 2

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How many atoms of Cu are present in 200 g of Cu? You have to expand your mind a bit on this one. Is there a direct conversion between numbers of atoms and grams of an element? NO! Well, what do we know that will help us, then? We know there are 6.02 X 10 23 atoms in a mole of something. We know 63.5 g of Cu is equal to one mole of Cu atoms. How can we use these two facts to help us solve the problem?

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How many atoms of Cu are present in 200 g of Cu? 1.Find out how many moles is equal to 200 g Cu. 2.Find out how many atoms there are in this many moles. 1. Molar mass Cu = 63.5 g/mol Use this as a proportion! 63.5 gCu 200 g Cu ------------ = -------------x = 3.15 moles Cu 1 mole x mole 2. There are 6.02 X 10 23 atoms of Cu in a mole of Cu. 6.02 X 10 23 atoms Cu x atoms Cu --------------------------- = ------------------- x = 1.9 X 10 24 atoms 1 mole Cu 3.15 moles Cu of Cu

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How many atoms of Cu are present in 200 g of Cu? 1mole Cu6.02 x 10 23 atoms Cu 200 g Cu x ------------- x -------------------------- = 63.5 g Cu 1 mole Cu A much shorter way…Dimensional Analysis! x = 1.9 X 10 24 atoms of Cu Menu

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The Mole toichiometry_notes.htm.

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