Test1-2009-solutions - Name: _ Student Number: _ CHEMISTRY...

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Name: ________________________ Student Number: _______________ Version 1 Page 1 CHEMISTRY 1E03 16 OCTOBER 2009 Instructor: J. Barbier MCMASTER UNIVERSITY - TERM TEST # 1 - DURATION: 100 minutes Answers for Version 1 1. Cl 2 (g) reacts with a solution of KI(aq) by oxidizing iodide ions into iodine, I 2 (aq). What volume of chlorine gas (in mL) , measured at 25.00°C and 1.00 atm, is needed to completely react with 25.0 mL of 0.200 M KI(aq)? A) 61.2 2 mks B) 122 0.5 mk C) 15.2 D) 30.6 0.5 mk E) 6.12 1 mk The balanced reaction is Cl 2 + 2 KI 2 KCl + I 2 25.0 mL of 0.200 M KI(aq) contains 5 10 -3 mole KI which requires 2.5 10 -3 mole Cl 2 PV = nRT V = nRT/P = 2.5 10 -3 x 0.08206 x 298.15 /1 = 0.0612 L = 61.2 mL 2. 29 Si is one of the istopes of silicon. For this isotope, select the correct number of protons, neutrons, electrons, and the atomic number (in that order) : A) 14, 29, 14, 14 1 mk B) 14, 15, 14, 29 C) 14, 15, 14, 14 2 mks D) 15, 14, 15, 14 E) 29, 29, 29, 14 See chapter 2 in textbook. In 29 Si, 29 = atomic mass number = # protons + # neutrons
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Name: ________________________ Student Number: _______________ Version 1 Page 2 3. How many grams of magnesium oxide, MgO , can be produced from 3.50 g of magnesium metal and 1.60 g of oxygen gas? A) 2.94 B) 5.20 C) 2.01 1 mk D) 4.03 2 mks E) 5.80 The balanced reaction is: Mg + ½ O 2 MgO 1.6 g O 2 (g) = 0.05 mole O 2 and 3.50 g Mg = 0.144 mole Mg. Hence O 2 is the limiting reagent. 0.05 mole O 2 yields 0.1 mole MgO, i.e. 4.03 g. 4. A sample of a barium salt weighing 0.676 g was completely dissolved in water and treated with an excess of sodium sulfate. A precipitate formed which was dried and weighed, yielding 0.4105 g. What is the mass percentage of barium in the original salt sample? A) 35.7 2 mks B) 58.8 C) 39.8 D) 24.1 E) 69.8 The precipitation reaction is Ba salt(aq) + Na 2 SO 4 BaSO 4 (s) + Na salt (aq) mass (BaSO 4 ) = 0.4105 g 0.4105/233.40 = 1.76 10 -3 mole BaSO 4 = 1.76 10 -3 mole Ba 2+ 1.76 10 -3 mole Ba 2+ = 0.2415 g Ba 0.2415 g (Ba)/0.676 g (sample) = 0.357 = 35.7% 5. Aqueous chromate ions, CrO 4 2– (aq), react with zinc metal in acidic solution to produce Cr 3+ (aq) and Zn 2+ (aq) ions. When the reaction is balanced with the smallest possible integers as stoichiometric coefficients, what is the coefficient for H 2 O ? A) 8 2 mks B) 6 C) 3 D) 9 E) 4 Balanced reaction: 16 H + + 2 CrO 4 2- + 3 Zn 8 H 2 O + 2 Cr 3+ + 3 Zn 2+
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Name: ________________________ Student Number: _______________ Version 1 Page 3 6. Select the false statement among the following: A) The hydrogenphosphate ion, HPO 4 2– , can act as a Bronsted acid. B) A total of 6 electrons are transferred during the following reaction as written: Na 2 Cr 2 O 7 (aq) + 6 CoSO 4 (aq) + 7 H 2 SO 4 (aq) Cr 2 (SO 4 ) 3 (aq) + 3 Co 2 (SO 4 ) 3 (aq) + 7 H 2 O(l) + Na 2 SO 4 (aq) C) Sodium hydride reacts with water to produce hydrogen gas. D)
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This note was uploaded on 02/05/2010 for the course PHYSICS 1D03 taught by Professor N. mckay during the Spring '08 term at McMaster University.

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Test1-2009-solutions - Name: _ Student Number: _ CHEMISTRY...

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