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Published byIsaac Montgomery Modified about 1 year ago

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Reminder: 1 mol of anything e.g. Oxygen, carbon, dollars, toys, etc. is 6.02 x 10 23

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Let’s look at this pile of carbon in the form of charcoal. I bet you there is a bunch of carbon moles in there. Let’s see how much.

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Now, this clump represents one mole. Can you estimate how many do you see in the whole bunch? Well, it’s hard to visualize. Let’s do some math. Since this is 1 mole, that means it weighs g. Why? Because, according to the periodic table, 1 mole of Carbon weighs g. Well, how many moles are present in this whole bunch? Let’s weigh it first.

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0.00 g12.01 g 6.02 x 10 23

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0.00 g So, we weigh the whole bunch and it turns out to be g g

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1 mol ? mol

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So, there are two ways to solve this problem: a)Use proportions b)Use the n= m / mMm a)Use proportions: Since1 mol of C=12.01 g ? mol=15.50 g ? mol=1 mol of Cx15.50 g g =1.29 mol

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b)Let’s use the formula n= m / mMm Step 1: What do we have? m: g mMm: g/mol N: ? Step 2: You can use a triangle mn: m. mMm n x mMmn: g g/mol n: 1.29 mol

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Another example: let’s say there are 4 moles of water in this beaker. How many grams would that be?

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Well, there are a couple of steps. We are trying to find the mass of 4 moles of water, we need the molar mass of water. Step 1: Find molar mass H 2 O: 2(1)+16=18 g/mol Step 2: Let’s find the mass, I’ll use the proportions method 1 mol of H 2 O=18 g 4 mol of H 2 O=? g ? g=4 mol of H 2 Ox18 g/mol 1 mol of H 2 O ? g=72 g What about the number of molecules?

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Well, for the number of molecules, let’s see what happens. 1 mol of H 2 O=6.02x10 23 molecules of H 2 O 4 mol of H 2 O=? molecules ? molecules=4 mol of H 2 O x (6.02 x molecules of H 2 O) 1 mol of H 2 O =2.408x molecules of H 2 O

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Okay, solve the following problems: a)How many moles of Ca(OH) 2 are present in a 200 g sample of Ca(OH) 2 ? b)How many molecules of MgF 2 are present in a 100 g sample of MgF 2 ?

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