475

24 Experiment 11. Oxidizing properties of nitrogen (III). Add 4–5 drops of sulfuric acid and 4–5 drops of sodium iodide to 4–5 drops of a solution of sodium nitrite NaNO 2. The liberated iodine is detected by the addition of a starch solution. Write the equation of the reaction, select the coefficients by the electronic balance method. Experiment 12. Reducing properties of nitrogen (III). Add 4–5 drops solution of sulfuric acidto 3–4 drops of sodium nitrite solution NaNO 2. Then add 5 drops of KMnO 4  solution. What’s happening? Write the equation of the reaction, arrange the coefficients by the electronic balance method. Experiment 13. Instability of thiosulfate in an acid medium . Add 5–6 drops of a solution of sodium thiosulfate Na 2 S 2 O 3  and 3–4 drops of a 1M solution of sulfuric acid to the tube. What is observed? Write the equation for the reaction of sodium thiosulfate with sulfuric acid. LESSON 11. ELECTRODE AND REDOX – POTENTIALS Required base level. Typical oxidants and reducing agents. The concept of a galvanic cell, electromotive force E mf . Calculation of the pH of strong and weak electrolytes. Questions for the preparation for the lesson. 1. Mechanism of the appearance of the electrode potential. Element of Daniel-Jacobi. The Nernst equation. 2. Oxidation-reduction system: types of oxidation-reduction systems. The Nernst-Peters equation. 3. The mechanism of occurrence of redox potential. Factors affecting redox potentials: the influence of the ligand environment of the central atom on the value of the redox potential. 4. Hydrogen electrode: device, application. The Nernst equation for the hydrogen electrode. E mf measurement with hydrogen electrode. Electrode- potential seriesof metals. 5. Ion-selective electrodes: glass electrode. The Nernst equation for a glass electrode. 6. Determination of pHvalue of solutions with hydrogen and glass electrodes. 7. E mf of electrochemical reactions. The constant of the oxidation-reduction process. Input test-control on the topic «Electrode and redox potentials».