tutorial 4a solutions (test 1 review)

tutorial 4a solutions (test 1 review) - CHEM 1E03 TUTORIAL...

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CHEM 1E03 TUTORIAL #4a Solutions _____________________________________________________________________ Version 1 Page 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 B) 122 C) 15.2 D) 30.6 E) 6.12 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. 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 D) 4.03 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. 3. 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 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%
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CHEM 1E03 TUTORIAL #4a Solutions _____________________________________________________________________ Version 1 Page 2 4. 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 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+ 5. Select the false statement among the following: A) The hydrogenphosphate ion, HPO 4 2– , can act as a Bronsted acid. B)
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tutorial 4a solutions (test 1 review) - CHEM 1E03 TUTORIAL...

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