Why is excess na2co3 added during iodine titration by hypo solution?

Excess Na2CO3 is added during iodine titration with a hypo (sodium thiOSulfate) solution to ensure that all available iodine is converted into iodide ions. This helps to maintain a stable and consistent reaction environment by preventing the reformation of iodine from iodide, which could lead to inaccuracies in the titration results. Additionally, the carbonate ions help to buffer the solution, stabilizing the pH and enhancing the overall reaction efficiency.