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Quiz 8 Bleach-solutions

Quiz 8 Bleach-solutions - Version 098/ABCAC Quiz 8 Bleach...

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Version 098/ABCAC – Quiz 8 Bleach – lyon – (51155) 1 This print-out should have 10 questions. Multiple-choice questions may continue on the next column or page – find all choices before answering. 1 2 3 4 5 6 7 AA AB AC AD BA BB BC 8 9 10 BACK NEXT BD CA CB CC CD 001 10.0points Liquid bleaches and powered bleaches have the same active ingredient as the bleach used in experiment 8. What is the active ingredient in most liquid bleaches and bleaching powders? 1. hypochlorite ion (ClO - ) correct 2. hydrogen peroxide (H 2 O 2 ) 3. chlorine (Cl 2 ) 4. sodium hydroxide (NaOH) 5. sodium dichromate (Na 2 Cr 2 O 7 ) Explanation: 002 10.0points An excess of KI was added to a 0 . 475 g sam- ple of bleach. The liberated iodine required 3 . 7 mL of 0 . 0504 M Na 2 S 2 O 3 solution for the titration to reach the end point. What is the oxidizing capacity of the NaClO in the bleach? The molar mass of NaClO is 74.5 g/mol. 1. 0 . 584958 % 2. 1 . 16992 % 3. 0 . 877437 % 4. 0 . 292479 % 5. 1 . 4624 % correct Explanation: Two moles of Na 2 S 2 O 3 are required for ev- ery mole of hypochlorite in the reaction. (0 . 0037 L Na 2 S 2 O 3 ) parenleftbigg 0 . 0504 Na 2 S 2 O 3 1 L Na 2 S 2 O 3 parenrightbiggparenleftbigg 1molNaC 2 mol Na 2 S Convert the moles of NaClO to grams of NaClO: ( 9 . 324 × 10 - 5 moles NaClO ) parenleftbigg 74 . 5 g NaClO 1 mol NaClO parenrightbigg = 0 . 0 thepercentagebymassofNaClO: % NaClO = 0 . 00694638 g 0 . 475 g × 100 = 1 . 4624 % This is the oxidizing capacity of the bleach. 003 10.0points For the forward redox reaction Cl 2 (g) + 2 NaOH(aq) NaCl(aq) + NaOCl(aq) + H 2 O( ) to prepare bleach, identify the substance re- duced by the change in oxidation numbers.
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