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Published byAbigail Robertson Modified about 1 year ago

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The Mole Chapter 10

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Formula Mass: Is what a single molecule “weighs” in amu’s (atomic mass units) Revision: So, 1 molecule of Water (H 2 O) weighs: 2 x 1.01 (for H) + 1 x 16.00 (for O) = 18.02 amu’s

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Example #2: What is the mass of 1 molecule of Sugar(Sucrose)? (C 6 H 12 O 6 ) C:6 x 12.01 = H: 12 x 1.01 = O: 6 x 16.00 = Do other examples? a)CO 2 b)(NH 4 ) 2 CO 3

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The Mole: First, let’s look at names that reflect numbers: 1 dozen = 1 baker’s dozen = 1 score = 1 gross =

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Let’s now focus on a particular isotope – Carbon-12 1 Carbon-12 atom weighs ______________ But this is an impractical measurement. We want to work in the mass unit of grams. So, how many atoms of Carbon-12 would it take to weigh 12.00 g.?

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Amadeo Avogadro (Italian, 1776-1856) calculated the number to be 6.022 x 10 23 and is also known as a So now, the average atomic mass number also represents how many grams that element would weigh if you had 1 mole of that substance.

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So, 1 mole of Water weighs: H:2 x 1.01 g/mole = 2.02 g/mole O: 1 x 16.00 g/mole = 16.00 g/mole This # is known as the _____________(mass of 1 mole) of Water. Examples. Calculate the Molar Mass of the following: a.) SO 2 b.) (NH 4 ) 3 PO 4

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Mole to Mass & Mass to Mole Conversions If we are given the # moles of a substance and we want to calculate how much it weighs (i.e. what’s its mass?), then we convert by using the _________________________! E.g. What is the mass of 1.50 moles of Water? 1.50 mol. Of H 2 O x 18.02g of H 2 O = 27.03g of H 2 O 1 1 mol. of H 2 O E.g.#2 What is the mass of 0.75 mol. Of Salt?

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Now, going the other way. How many moles are in 100.g of CO 2 ? 100.g of CO 2 x 1 mol. of CO 2 = _______________ 1 44.01g of CO 2 E.g.#2 How many moles are in a pound of Sugar?

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Converting from moles to molecules & vicy versi In these conversions, instead of using the _________________________, you use Avacado’s Avagadro’s Number. (N A ) Ex. How many molecules are in 1.50 moles of Water? (remember: 1 mole = 6.02 x 10 23 ) 1.50 mol. x 6.02 x 10 23 molecules = ___________________ 1 1 mol. Ex.2) How many moles in 2.107 x 10 24 molecules of Salt? 2.107 x 10 24 molecules x ____ = 3.50 moles 16.02 x 10 23 molecules

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Do these in-class egg samples: 1.)How many molecules are in 0.02 moles of Sugar? 2.)How many moles are in 3.01 x 10 23 molecules of O 2 ? Let’s look at lots of molecules of Water.

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Time to draw a MOLE diagram I know what you’re thinking! Now we can do Mass to Molecules conversions & vicy versi. (Hint: it’s a 2 step Chain Method) Ex. How many molecules are in 12.0g (~½ oz) of Water? 12.0g of H 2 O x _____________x________________________ 1 1 mol of H 2 O = 4.00 x 10 23 molecules of H 2 O Ex. What does 9.03 x 10 22 molecules of Vitamin C weigh? (Vitamin C = C 6 H 8 O 6 )

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The Volume occupied by 1 mole of a gas is the Molar Volume. The Volume occupied by 1 mole of a gas @ STP is known as the Standard Molar Volume of a gas and is equal to 22.4 L. @ STP V = 22.4 L/mol. V = n x 22.4 L/mol. n So 1 mole of any gas occupies 22.4L @ STP, but their masses may be different. Standard Molar Volume

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So 2 moles of a gas will occupy twice the space (Volume) of 1 mole. e.g. 2H 2 + O 2 2H 2 O (more examples: N 2 + H 2 NH 3,…) And remember:1 mole = 6.02 x 10 23 molecules

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(Diagram – New Mole Diagram)

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Add that to the mole diagram… Mass (Grams) Mole Volume @STP Molecules/ Atoms

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