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HELP CENTER SCHEDULE STUDY GROUP SURVEY- CHECK YOUR EMAIL! LAB POTASSIUM HYDROXIDE SUB’D FOR SODIUM HYDROXIDE IN OLD VERSION OF PRE-LAB YOU DON’T NEED AN ALUMINUM CAN Announcements

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Which compound in the following list is NOT possible? 1. CaBr 2 2. KI 3. Al 2 O 4. LiCl 5. MgO

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Which compound is NOT ionic? (Which one is a molecular compound?) 1. LiCl, lithium chloride 2. SO 2, sulfur dioxide 3. AlF 3, aluminum fluoride 4. Ba(NO 3 ) 2, barium nitrate 5. NaHCO 3, sodium hydrogen carbonate

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Which compound formula name is NOT correct? 1. CaSO 4, calcium sulfate 2. NaNO 3, sodium nitrate 3. MgI 2, magnesium iodide 4. NH 4 PO 4, ammonium phosphate 5. Ca(ClO) 2, calcium hypochlorite

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Sodium oxalate has the formula Na 2 C 2 O 4. Based on this information, what is the formula for iron (III) oxalate? 1. FeC 2 O 4 2. Fe(C 2 O 4 ) 2 3. Fe(C 2 O 4 ) 3 4. Fe 2 (C 2 O 4 ) 3 5. Fe 3 (C 2 O 4 ) 2

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Chapter 3- Stoichiometry Stoichiometry= Compound stoichiometry quantitative (mass) relationships among elements in compounds Reaction stoichiometry the quantitative relationships among substances as they participate in chemical reactions

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The Mole Connects macroscopic to atomic world Atoms are really small- a measurable quantity of matter contains A LOT of atoms 1 dozen = 12 objects 1 mole = 6.022 x 10 23 objects 6.022 x 10 23 is called Avogadro’s number Unit sign: mole=mol

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Why is the mole a convenient unit for us to use? The mass of 1 mol of an element is equal to its atomic mass in grams Molar mass is in g/mol Molar mass of lithium= 6.939 g/mol

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How do we use it? Conversion factors Avogadro’s number Molar Mass

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1. How many atoms are in 0.7 mol of Ar? 2. How many moles do 3.00 x 10 20 atoms of B make? 3. How many moles do 41.0g of C make? 4. How many moles do 41.0g of He make? 5. What is the mass of 1 platinum (Pt) atom? Examples

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What is the mass of 2.60 mol of O? 1. 8.90 g 2. 0.163 g 3. 2.60 g 4. 41.6 g

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How many C atoms are in a 0.96-carat diamond? (1 carat=0.2g) Example

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Compounds and Moles 1 mole of a compound contains 6.022 x 10 23 molecules or “units” Molar mass = sum of atomic molar masses H 2 O CO 2 Fe(NO 3 ) 3

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Consider UF 6 What is the molar mass? How many grams in 0.5 mol? How many molecules in 0.5 mol? How many U atoms in 0.5 mol? How many F atoms in 0.5 mol? Example

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Molecular vs. Nonmolecular compound terms 1 mol CO 2 contains 6.022 x 10 23 molecules 1 mol NaCl contains 6.022 x 10 23 formula units

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Percent Composition The fraction of mass due to an element

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Determining Formulas from % Composition The ratio of atoms in the formula is the same as the ratio of moles of those elements. If you determine the ratio of moles, you know the formula. However, the formula determined is the empirical formula.

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1. What is the % composition of H in H 2 O 2 ? 2. Which of the following has the highest % composition of copper, Cu? (Don’t use a calculator) CuSO 4 Cu 2 SO 4 CuCO 3 Cu 2 CO 3 3. A compound has Ca, S, and O. What is the empirical formula? Ca:29.45% S:23.55% O:47.00% Examples

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Empirical vs. Molecular Formulas Example: Ethene is C 2 H 4 Percent composition tells us mol H/mol C = 2 The empirical formula is CH 2. The molecular formula is C 2 H 4.

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Example: A hydrocarbon has 82.65% C and 17.34% H Molar mass is 58.12 g/mol What are the empirical and molecular formulas?

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Hydrated Compounds Solids in which molecules of water are trapped and become part of the compound. Ex: Gypsum: CaSO 4 2H 2 O is hydrated calcium sulfate CaSO 4 is anhydrous calcium sulfate

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Determining the number of waters of hydration 1.023 g CuSO 4 x H 2 O is heated to drive off the water. The resulting anhydrous CuSO 4 has a mass of 0.654 g. What is the value of x?

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