is brought to a final volume of 1 L. Cap the flask and mix the contents thoroughly. ■ PRELAB GUIDING QUESTIONS/SIMULATIONS Prelab Part I The prelab assessment is designed to be completed by students independently or in small groups as they read the Explanation to Strengthen Student Understanding section. It will prepare them for developing their own procedure, analyzing their data, and performing lab calculations. After students complete the prelab assessment, their individual or small group responses should be discussed with the entire class.
175 OXIDATION-REDUCTION TITRATION TEACHER TIP You may wish to have students work on these questions for homework so that time in class can be spent solely on discussion. Depending on what content has been covered prior to this lab, you may choose to give students skeleton half-reactions to balance for Questions 2–6. If you choose to do this, Question 7 is recommended for in-class discussion only. If reduction potentials have been studied, you may elect to have students use a table of standard reduction potentials to answer Questions 2–7. 1. What measuring devices are used to obtain precise measurements of volumes? What measuring devices are used to obtain approximate measurements of volumes? 2. Write a balanced half-reaction for the reduction of permanganate ions in acidic solution. What are the oxidation states of manganese in this reaction? 3. Write a balanced half-reaction for the oxidation of hydrogen peroxide. What are the oxidation states of oxygen in this reaction? 4. What is the balanced reaction for the reduction of permanganate ions by hydrogen peroxide? How many electrons are transferred in this reaction? 5. Write a balanced half-reaction for the oxidation of iron (II) ions. Fe 2+ ( aq ) → Fe 3+ ( aq ) + e – 6. Write a balanced half-reaction for the reduction of permanganate ions by iron (II) ions. How many electrons are transferred in this reaction?
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