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Unit 7: The Mole (Chapter 10)

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The Mole (Ch. 10) I. Chemical Measurements (10-1) A. Atomic Mass & Formula Mass A. Atomic Mass & Formula Mass 1. The mass of atoms are so small (2.7 x 10^- 23 g) a relative mass scale was set up. 2. Based on the mass of carbon being 12 exactly. 3. The “made up” units to measure the mass of atoms (atomic mass) are called: amu

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4. Formula Mass: the sum of the atomic masses of all the atoms in a compound 5. Examples- determine the atomic or formula mass for the following (in amu’s): a. Bromine (Br): ______ b. Gold (Au): ______ c. Sulfur Dioxide (SO2): ______ d. Carbonic Acid (H2CO3): ______ e. Acetic Acid (HC2H3O2): ______ f. Lead (II) Phosphate [Pb3(NO3)2]: _______

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B. What is a Mole? 1. Since atoms are so small and we deal with so many at a time, two things were developed: a. Mole: the number of atoms of an element equal to the number of elements in exactly 12.0 grams of carbon-12. b. Avogadro’s Number: refers to the amount of: 6.02 x 10^23 --> (of anything) * Note – a mole of anything contains 6.02 x 10^23

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C. Molar Mass 1. Molar Mass: the mass of 1 mole of anything a. The number of items in a mole of substance is the same, the mass varies. b. The molar mass is equal to the atomic, molecular, or formula mass. 2. Example – determine the molar mass for: - Calcium Chloride (CaCl2): ________ - Glucose (C6H12O6): _________

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II. Mole Conversions (10-2) - See Example Problem Sheet A. Moles to grams 1. Determine the molar mass 2. Use conversion: molar mass of X (g) = 1 mole X; where X is anything 3. Examples a. What is the mass of 2.5 moles of NaCl? a. What is the mass of 2.5 moles of NaCl? b. What is the mass of 3.75 moles of calcium hydroxide? b. What is the mass of 3.75 moles of calcium hydroxide?

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B. Grams to moles 1. Determine the molar mass 2. Use conversion: molar mass of X (g) = 1 mole; where X is anything 3. Examples: a. How many moles of carbon are in a sample with the mass of 24 grams? a. How many moles of carbon are in a sample with the mass of 24 grams? b. How many moles of NaNO3 are in 7.57 grams of sample? b. How many moles of NaNO3 are in 7.57 grams of sample?

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C. Moles to number of units 1. Use conversion: 1 mole = 6.02 x 10^23 units 2. Examples: a. How many molecules are in a 2-mole sample of C? a. How many molecules are in a 2-mole sample of C? b. How many molecules are in a sample of.0891 moles of NaNO3? b. How many molecules are in a sample of.0891 moles of NaNO3?

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D. Number of units to moles 1. Use conversion: 1 mole = 6.02 x 10^23 units 2. Examples: a. How many moles of NaOH are in a sample with 2.76 x 10^23 molecules of NaOH? a. How many moles of NaOH are in a sample with 2.76 x 10^23 molecules of NaOH?

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E. Grams to number of units 1. Determine molar mass 2. Convert grams to moles 3. Convert moles to units 4. Examples: a. How many molecules of NaNO3 are in a sample of 7.57 grams of NaNO3? b. How many molecules are in a sample of oxygen (O2) gas with a mass of 64 grams?

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F. Number of units to grams 1. Determine molar mass 2. Convert units to moles 3. Convert moles to grams 4. Examples: a. How many grams of NaOH are in a sample with 2.76 x 10^23 molecules? b. How many grams of NaCl are in a sample with 4.56 x 10 ^24 molecules?

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