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hw 02 - baum(awb464 H02 Stoichiometry Mccord(50970 This...

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baum (awb464) – H02: Stoichiometry – Mccord – (50970) 1 This print-out should have 29 questions. Multiple-choice 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. (NH 4 ) 2 SO 4 2. CaOH correct 3. Ba 3 (PO 4 ) 2 4. Mg(OH) 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. CoO. 2. Co 3 O 2 . 3. Co 3 O. 4. CoO 3 . 5. Co 2 O 3 . correct 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 2. AlH 3 3. Al(OH) 3 correct 4. AlOH 3 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. KCr 2 O 7 3. KCrO 3 4. K 2 Cr 5. KCrO 4 6. K 2 Cr 3

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baum (awb464) – H02: Stoichiometry – Mccord – (50970) 2 7. K 2 CrO 4 8. K 2 Cr 2 O 7 correct Explanation: 005 10.0 points How many atoms are in 0 . 0309 mol K? Correct answer: 1 . 8608 × 10 22 atoms. Explanation: n K = 0 . 0309 mol n K = ? atoms 0 . 0309 mol K × 6 . 022 × 10 23 atoms K mol K = 1 . 8608 × 10 22 atoms K 006 10.0 points Which one has the greatest number of atoms? 1. All have the same number of atoms 2. 3.05 moles of argon 3. 3.05 moles of CH 4 correct 4. 3.05 moles of water 5. 3.05 moles of helium 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: ? atoms = 3 . 05 mol He × 6 . 02 × 10 23 atoms 1 mol = 1 . 84 × 10 24 atoms For 3.5 moles of argon: ? atoms = 3 . 05 mol Ar × 6 . 02 × 10 23 atoms 1 mol = 1 . 84 × 10 24 atoms 007 10.0 points Each mole of Al(NO 3 ) 3 contains how many moles of oxygen atoms?
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