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F10Q3W4 - CHEM 0110 QUIZ 3 WEEK 4 MONDAY 1:00 PM NAME 1 For...

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CHEM 0110 QUIZ 3 WEEK 4 MONDAY, 1:00 PM September 20, 2010 NAME_______________________________________________________________________ 1. For each of the following, state whether the name is correct or incorrect for the given formula. Give your reasoning. Give the correct names where needed. a) NiSO 4 : Nickel sulfide b) CO 2 : carbon dioxide c) CaBr 2 : Calcium dibromide 2. a) Calculate the mass of (exactly) 8 molecules of H 2 S. Does the magnitude of your answer make sense? Give your reasoning. b) How many H atoms are contained in 8 molecules of H 2 S? Avogadro's constant = 6.02 x 10 23 /mol. You can use information on the periodic table. ANSWERS 1. a) Two errors. This is a sulfate, not sulfide; also a Roman numeral is needed: Nickel(II) sulfate b) Correct c) As this is ionic, no Greek prefix should be given: Calcium bromide 2. a) Many possible approaches. For instance: Mass = 8 molec x mol 1 34.08g x molec 10 x 6.02 mol 1 23 = 4.53 x 10 -22 g The mass is very small, as expected for a small number of molecules. b) # of H atoms = 8 molec of H 2 S x molec S H 1 atom H 2 2 = 16 H atom For Make-up Only Regular recitation Day: Time: instructor: Quiz Score: Group score: Scores recorded by:
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CHEM 0110 QUIZ 3 WEEK 4 MONDAY, 6:00 PM September 20, 2010 NAME_______________________________________________________________________ 1. a) Write a balanced equation for the reaction of solid iron(III) oxide with hydrogen gas to form solid elemental iron. There is one additional product species. b) Identify all the molecular species in the equation 2. In lab experiment #1, you heated a solution of hydrated cobalt(II) chloride, CoCl 2 .6H 2 O. a) What is the molar mass of CoCl 2 .6H 2 O? b) Determine the number of moles in a 1.034g sample of CoCl 2 .6H 2 O. c) Determine the number of moles of H 2 O in 3 moles of CoCl 2 .6H 2 O Show your work. You can use information on the periodic table. ANSWERS 1. a) As oxygen (from the iron oxide) and hydrogen have not been accounted for in the products, it is most likely that water is the other product. Fe 2 O 3 (s) + 3 H 2 (g) 2 Fe(s) + 3 H 2 O(g) b) Molecular species: H 2 and H 2 O. Note: Fe 2 O 3 has been named with a Roman numeral and thus must be ionic. 2. a) Molar mass = 58.93 + 2(35.45) + 6(2x1.008 + 16.00) g/mol = 237.9 g/mol b) # of moles = 1.034g x 237.9g mol 1 = 4.35 x 10 -3 mol c) # of moles of H 2 O = 3 moles of CoCl 2 .6H 2 O x 2 2 2 6 moles of H O 1 mol CoCl .6H O = 18 mol H 2 O For Make-up Only Regular recitation Day: Time: instructor: Quiz Score: Group score: Scores recorded by:
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CHEM 0110 QUIZ 3 WEEK 4 TUESDAY, 8:00 AM September 21, 2010 NAME_______________________________________________________________________ 1. The formula of iron(III) thiosulfate is Fe 2 (S 2 O 3 ) 3 . Deduce the charge on the thiosulfate ion. Give your reasoning . 2. Name the following compounds: Cr 2 O 3 ; B 2 O 3 3. (a) Calculate the number of N atoms in 5 formula units of Co(NO 3 ) 2 . (b) Calculate the number of O atoms in exactly 5 mol of Co(NO 3 ) 2 . Avogadro's number = 6.02 x 10 23 /mol. ANSWERS 1. From the name, we conclude that iron has a +3 charge in this compound. From the 2:3 ratio of Fe to thiosulfate in the formula, we conclude that the charge on the thiosulfate ion is -2.
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