AssignmentSevenKey

# AssignmentSevenKey - Take-Home Assignment#7 1 Solutions of...

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Take-Home Assignment #7 1. Solutions of perchloric acid, HClO 4 , may be standardized by titrating against a primary standard of sodium carbonate, Na 2 CO 3 . Typically, the titration is carried out to the carbonate ion’s second endpoint. Suggest a mass of Na 2 CO 3 to use if you are standardizing a solution of HClO 4 whose concentration is within the range of 0.145 M to 0.155 M and you wish to use between 35 mL and 45 mL of titrant. The reaction between HClO 4 and Na 2 CO 3 will be 2HClO 4 + Na 2 CO 3 products The lower limit for the mass of Na 2 CO 3 will be with 35 mL of 0.145 M HClO 4 and the upper limit will be with 45 mL of 0.155 M HClO 4 . For the lower limit 3 2 3 2 3 2 4 3 2 4 4 CO Na g 0.27 CO Na mol CO Na g 105.99 HClO mol 2 CO Na mol 1 HClO L 0.035 HClO M 0.145 = × × × A similar calculation for the upper limit gives 0.37 g Na 2 CO 3 . 2. A 50.00–mL sample of white grape juice requires 21.48 mL of 0.03776 M NaOH to achieve a visual endpoint. Express the acidity of the grape juice as grams of tartaric acid, H 2 C 4 H 4 O 6 , per 100 mL. Assume that both of tartaric acid’s acidic protons are titrated at the titration’s endpoint. The titration reaction is

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AssignmentSevenKey - Take-Home Assignment#7 1 Solutions of...

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