Topic: Iodometry
1. the reason why the Cu2+ solution has to be titrated immediately after addition of KI
- I thought, because if allowed to stand for a long time, iodine will volatilize and a change in concentration of iodine will occur...is this right? Please correct me if I'm wrong. Thank you in advance
You are correct but there are other reasons, too.
These titrations, in which the liberated iodine is titrated, is done in the presence of KI. Air will oxidize the I^- to free I2 also; therefore, high results will occur because of the excess I2. A third reason is that any organic material present will be oxidized by I2.
Yes, you are partially correct. One reason why the Cu2+ solution needs to be titrated immediately after the addition of KI is to prevent the volatilization of iodine. If the solution is allowed to stand for a long time, iodine can escape into the air and the concentration of iodine will decrease, leading to inaccurate results.
However, there are other reasons for titrating the solution immediately. One reason is that the presence of air can cause the iodide ions (I-) to be oxidized to free iodine (I2). This oxidation reaction can lead to an excess of iodine in the solution, resulting in higher titration results.
Another reason is that any organic materials present in the solution can react with the iodine. Iodine is a strong oxidizing agent and can cause oxidation of organic substances, which may interfere with the titration process and lead to inaccurate measurements.
In summary, immediate titration after adding KI is essential to prevent volatilization of iodine, minimize the oxidation of iodide ions to free iodine by air, and prevent potential interference from oxidation reactions with organic materials.