1. What are the pertinent chemical equations in the standardization of sodium thiosulfate solution? 2. Explain the reason for the addition of H2SO4 and excess KI. 3. What is the effect of adding the acid before KI? 4. Present the pertinent chemical equations involved in the analysis. 5. Explain the stepwise production of titratable l2 from dissolved O2 in the sample. 6. Explain why the reagents are added in the specific sequence described in the experiment.