posted by smiley .
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.