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Unformatted text preview: goldstein (ddg625) – H02: Stoichiometry – Mccord – (50970) 1 This printout should have 29 questions. Multiplechoice questions may continue on the next column or page – find all choices before answering. This assignment comes from Chapters 2 and 3 in your book. Nomenclature (the nam ing of compounds, etc...) is in Chapter 2. Chapter 3 is on stoichiometry. You need to know how to calculate all the types of prob lems on this homework. ALEKS does do this well. READ Chapter 3 and LOOK at the ex amples. This is important although I will not formally cover it in class. You are expected to know this already. 001 10.0 points Which compound has the wrong chemical for mula? 1. Mg(OH) 2 2. (NH 4 ) 2 SO 4 3. CaOH correct 4. Ba 3 (PO 4 ) 2 Explanation: The calcium ion is Ca 2+ ; the hydroxide ion is OH . Two OH are needed to balance the charge of each Ca 2+ , so the formula is Ca(OH) 2 . The magnesium ion is Mg 2+ ; the hydroxide ion is OH . Two OH are needed to balance the charge of each Mg 2+ , so the formula is Mg(OH) 2 . The barium ion is Ba 2+ ; the phosphate ion is PO 3 4 . Two PO 3 4 are needed to balance the charge of every three Ba 2+ . (This gives a total anion charge of 6 and a total cation charge of +6.) The formula is Ba 3 (PO 4 ) 2 . The ammonium ion is NH + 4 ; the sulfate ion is SO 2 4 . Two NH + 4 are needed to balance the charge of each SO 2 4 , so the formula is (NH 4 ) 2 SO 4 . 002 10.0 points Cobalt(III) oxide would be the label for 1. Co 2 O 3 . correct 2. Co 3 O. 3. CoO. 4. Co 3 O 2 . 5. CoO 3 . Explanation: The cobalt(III) ion is Co 3+ ; the oxide ion is O 2 . Three O 2 are needed to balance the charge of every two Co 3+ . (This gives a total cation charge of +6 and a total anion charge of 6.) The formula is Co 2 O 3 . 003 10.0 points Give the formula for aluminum hydroxide. 1. AlOH 3 2. AlOH 3. AlH 3 4. Al(OH) 3 correct Explanation: The aluminum ion is Al 3+ ; the hydroxide ion is OH . Three OH are needed to balance the charge of each Al 3+ , so the formula is Al(OH) 3 . 004 10.0 points Choose the formula for the compound potas sium dichromate. 1. K 2 Cr 3 O 4 2. KCrO 4 3. K 2 Cr 2 O 7 correct 4. KCrO 3 5. K 2 Cr 3 6. K 2 Cr goldstein (ddg625) – H02: Stoichiometry – Mccord – (50970) 2 7. KCr 2 O 7 8. K 2 CrO 4 Explanation: 005 10.0 points How many atoms are in 0 . 0464 mol K? Correct answer: 2 . 79421 × 10 22 atoms. Explanation: n K = 0 . 0464 mol n K = ? atoms . 0464 mol K × 6 . 022 × 10 23 atoms K mol K = 2 . 79421 × 10 22 atoms K 006 10.0 points Which one has the greatest number of atoms? 1. 3.05 moles of argon 2. 3.05 moles of water 3. 3.05 moles of CH 4 correct 4. 3.05 moles of helium 5. All have the same number of atoms Explanation: For 3.05 moles of water: ? atoms = 3 . 05 mol H 2 O × 6 . 02 × 10 23 molec 1 mol × 3 atoms 1 molecule = 5 . 51 × 10 24 atoms For 3.05 moles of CH 4 : ? atoms = 3 . 05 mol CH 4 × 6 . 02 × 10 23 molec 1 mol × 5 atoms 1 molecule = 9 . 18 × 10 24 atoms For 3.05 moles of helium:For 3....
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 Fall '07
 Fakhreddine/Lyon
 Chemistry, Mole, Stoichiometry, mol, mol Co

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