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Chemical Quantities

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Describe the concept of the mole and its importance to measurement in chemistry. Calculate the mass of compounds in atomic mass units. Calculate the molar mass of various substances. Additional KEY Terms Avogadro’s number

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Avogadro ( ) Any sample of any gas at the same temperature and pressure will contain the same number of particles. Defined 22.4 L as the molar volume for any gas. Particles are now counted in moles (n).

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The molecular mass of water (H 2 O) is 18.0 µ... One mole of any particle has a mass equal to its total formula mass – IN GRAMS. The mass of 1 atom of Al = 27.0 µ The mass of 1 mole of Al atoms = 27.0 g So...the molar mass of water is 18.0 g/mol. The mass of 1 mole is the molar mass - (g/mol)

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What is the molar mass of ammonium dichromate? Determine the molar mass. 1 mole of (NH 4 ) 2 Cr 2 O 7 = 2 N + 8 H + 2 Cr + 7 O = 2(14.0 g/mol )+ 8(1.0 g/mol )+ 2(52.0 g/mol )+ 7(16.0 g/mol ) (NH 4 ) 2 Cr 2 O 7 = g/mol (NH 4 ) 2 Cr 2 O 7

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Mole Questions And Dimensional Analysis

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Rules for using a Dimensional Analysis 1. Start with what you know 2. Put ratio units you want to cancel on bottom 3. Put ratio units you need on the top 4. Multiply across the top, Divide across the bottom 8 slice 250 pepperoni 4 pepperoni 1 slice 1 pizza How many pizzas would 250 pieces of pepperoni make? = 7.8 Pizzas

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What is the mass of 1.20 x 10 –5 moles of carbon tetrachloride, CCl 4 ? CCl 4 =1 C + 4 Cl = 1(12.0 g/mol) + 4(35.5 g/mol) =154.0 g/mol or g 1 mole 1.20 x mol 1 mol g 1 mole 1.85 x g

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Calculating the Number of Particles

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We call this - Avogadro's Number In one mole there is 6.02 x particles x pencils is 1 mole of pencils 6.02 x carbon atoms is 1 mole… 6.02 x water molecules is 1 mole… The term "particle" refers to any individual thing like atoms, formula units, molecules, ions, etc. or 6.02 x particles 1 mole 6.02 x particles 1 mole

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How many atoms in 25.0 moles of copper? 25.0 mol Cu 1.51 x atoms = How many molecules of water in 1.50 x 10 –5 moles? = 9.03 x molecules of water 1.50 x 10 –5 mol H 2 O 6.02 x particles 1 mole 6.02 x particles 1 mole

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How many moles is 5 atoms of zinc? 5 atoms of Zinc is 8.31 x 10 –24 moles. 5 atoms Zn = 8.31 x moles 6.02 x particles 1 mole

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The mole allows the conversion between mass and number of particles.

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How many molecules of water in a 10.0 g sample of water? mol H 2 0 = 1 mole 18.0 g 10.0 g H 2 O mol H 2 O 6.02 x particles 1 mole = 3.34 x molecules H 2 0

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Put the two equations together There are 3.34 x molecules in 10.0 g of water. 1 mole 6.02 x particles of H 2 O 10.0 g H 2 O 18.0 g 1 mole = 3.34 x molecules H 2 0

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How many atoms in 25.0 g of sodium chloride? NaCl = 58.5 g/mol = 5.14 x atoms 1 mole 6.02 x For.U 25.0 g NaCl 58.5 g 1 mole 2 atoms 1 For. U

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CAN YOU / HAVE YOU? Describe the concept of the mole and its importance to measurement in chemistry. Calculate the mass of compounds in atomic mass units. Calculate the molar mass of various substances. Additional KEY Terms Avogadro’s number

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