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Unformatted text preview: gonzales (pag757) Pre-lab 2 Lyon (52635) 1 This print-out should have 13 questions. Multiple-choice questions may continue on the next column or page find all choices before answering. This pre-lab assignment is due by 8AM on the day of your next lecture class. This pre- lab covers material in experiment 2. 001 (part 1 of 2) 10.0 points What is the purpose of using potassium car- bonate in the experimental procedure? 1. The solution is not acidic enough after adding HCl, so we have to add potassium carbonate to finish dissolving the calcium. 2. The potassium carbonate increases the yield of all three components in the mixture. 3. The larger potassium ions wrestle chloride ions from the smaller sodium ions, thereby removing sodium from solution. 4. The carbonate ions react with calcium ions in solution to form a solid CaCO 3 precip- itate. correct Explanation: 002 (part 2 of 2) 10.0 points What is the principal product formed when potassium carbonate is added to the sam- ple? (Check your lab manual for the relevent chemical equation.) 1. calcium chloride precipitate 2. carbon dioxide and water 3. potassium chloride precipitate 4. calcium carbonate precipitate correct Explanation: 003 (part 1 of 2) 10.0 points What is the purpose of adding hydrochloric acid in the experimental procedure? 1. HCl is not used in the experimental pro- cedure. 2. HCl combines with NaCl to form Cl 2 gas. 3. HCl reacts with calcium carbonate, caus- ing it to dissolve. correct 4. The acidic HCl prevents NaCl from turn- ing into basic NaOH....
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- Spring '10