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What is the issue to pay attention to in indirect iodometric method? Give the answer on the 10th floor!
You need to add an indicator - the starch also needs to be protected from light, I can't remember anything else.
Indirect iodometry is mostly performed in neutral or weakly acidic solutions.
The time to add the starch indicator should be controlled. Adding the indicator too early can cause the starch to absorb too much iodine.
Indirect iodometric method I- is a medium strength reducing agent. Mainly used to measure: E0'(E0)
1. KI must be overdosed. 2. Add H2SO4 to maintain acidic conditions in the solution, but do not use HCL.
For measuring copper. Add HCL to form - complex.
Answer: The starch indicator should be added near the end point. Adding starch too early will absorb excess iodine, so most of the iodine should be reacted first to reduce errors. The other answers are all correct, but I personally think this is the most important! hehe!
Without an indicator, how do you know it's near the end? ? ? ?
After adding iodine, it will appear red or yellow. When the titration reaches light yellow, it means that the end point is near. Add starch again and continue titrating until the blue color disappears as the end point! This post was last edited by zjs0536 on 2009-4-2 12:18 ]
I guess what the poster said is that it should be placed in a dark place when it is left to stand, and the sealing should be good, that is, it should use a bell-mouthed iodine bottle, and then seal the area around the stopper with water before placing it in a dark place.
The amount of KI should be sufficient, and the reaction should be sealed in water for ten minutes in the dark. Do not add the starch indicator too early, and the coefficient must be accurate in the calculation.