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1 Chapter 6 Chemical Quantities

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2 How you measure how much? How you measure how much? n You can measure mass, n or volume, n or you can count pieces. n We measure mass in grams. n We measure volume in liters. n We count pieces in MOLES.

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3 Moles n Defined as the number of carbon atoms in exactly 12 grams of carbon- 12. n 1 mole is 6.02 x 10 23 particles. n Treat it like a very large dozen n 6.02 x 10 23 is called Avogadro’s number.

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4 Representative particles n The smallest pieces of a substance. n For a molecular compound it is a molecule. n For an ionic compound it is a formula unit. n For an element it is an atom.

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5 Types of questions n How many oxygen atoms in the following? –CaCO 3 –Al 2 (SO 4 ) 3 n How many ions in the following? –CaCl 2 –NaOH –Al 2 (SO 4 ) 3

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6 Types of questions n How many molecules of CO 2 are the in 4.56 moles of CO 2 ? n How many moles of water is 5.87 x 10 22 molecules? n How many atoms of carbon are there in 1.23 moles of C 6 H 12 O 6 ? n How many moles is 7.78 x 10 24 formula units of MgCl 2 ?

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7 Measuring Moles n Remember relative atomic mass? n The amu was one twelfth the mass of a carbon 12 atom. n Since the mole is the number of atoms in 12 grams of carbon-12, n the decimal number on the periodic table is also the mass of 1 mole of those atoms in grams.

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8 Gram Atomic Mass n The mass of 1 mole of an element in grams. n 12.01 grams of carbon has the same number of pieces as 1.008 grams of hydrogen and 55.85 grams of iron. n We can write this as 12.01 g C = 1 mole n We can count things by weighing them.

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9 Examples n How much would 2.34 moles of carbon weigh? n How many moles of magnesium in 24.31 g of Mg? n How many atoms of lithium in 1.00 g of Li? n How much would 3.45 x 10 22 atoms of U weigh?

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10 What about compounds? n in 1 mole of H 2 O molecules there are two moles of H atoms and 1 mole of O atoms n To find the mass of one mole of a compound –determine the moles of the elements they have –Find out how much they would weigh –add them up

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11 What about compounds? n What is the mass of one mole of CH 4 ? n 1 mole of C = 12.01 g n 4 mole of H x 1.01 g = 4.04g n 1 mole CH 4 = 12.01 + 4.04 = 16.05g n The molecular mass of CH 4 is 16.05g n The mass of one mole of a molecular compound.

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12 Gram Formula Mass n The mass of one mole of a compound. n Calculated the same way. n What is the GFM of Fe 2 O 3 ? n 2 moles of Fe x 55.85 g = 111.70 g n 3 moles of O x 16.00 g = 48.00 g n The GFM = 111.70 g + 48.00 g = 159.70g

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13 Molar Mass n The generic term for the mass of one mole. n The same as molecular mass, gram formula mass, and gram atomic mass.

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14 Examples n Calculate the molar mass of the following and tell me what type it is. n Na 2 S nN2O4nN2O4nN2O4nN2O4 nCnCnCnC n Ca(NO 3 ) 2 n C 6 H 12 O 6 n (NH 4 ) 3 PO 4

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15 Using Molar Mass Finding moles of compounds Counting pieces by weighing

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16 Molar Mass n The number of grams of 1 mole of atoms, ions, or molecules. n We can make conversion factors from these. n To change grams of a compound to moles of a compound.

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17 For example n How many moles is 5.69 g of NaOH?

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18 For example n How many moles is 5.69 g of NaOH?

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19 For example n How many moles is 5.69 g of NaOH? l need to change grams to moles

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20 For example n How many moles is 5.69 g of NaOH? l need to change grams to moles l for NaOH

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21 For example n How many moles is 5.69 g of NaOH? l need to change grams to moles l for NaOH l 1mole Na = 22.99g 1 mol O = 16.00 g 1 mole of H = 1.01 g

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22 For example n How many moles is 5.69 g of NaOH? l need to change grams to moles l for NaOH l 1mole Na = 22.99g 1 mol O = 16.00 g 1 mole of H = 1.01 g l 1 mole NaOH = 40.00 g

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23 For example n How many moles is 5.69 g of NaOH? l need to change grams to moles l for NaOH l 1mole Na = 22.99g 1 mol O = 16.00 g 1 mole of H = 1.01 g l 1 mole NaOH = 40.00 g

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24 For example n How many moles is 5.69 g of NaOH? l need to change grams to moles l for NaOH l 1mole Na = 22.99g 1 mol O = 16.00 g 1 mole of H = 1.01 g l 1 mole NaOH = 40.00 g

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25 Examples n How many moles is 4.56 g of CO 2 ? n How many grams is 9.87 moles of H 2 O? n How many molecules in 6.8 g of CH 4 ? n 49 molecules of C 6 H 12 O 6 weighs how much?

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