The dissolution of iodine crystals with potassium iodide is very slow. To prepare a 0.005 M Iodine solution will require you keep the vessel until all crystals dissolve. With the low concentration and the volatile nature of Iodine, the solution might lose its concentration at the time of complete dissolution. Can the solution be heated to speed up the dissolution?
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1 Answer
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Since $\ce{I2}$ is a non-polar covalent molecule, it does not ionize in water. It cannot also be soluble in the polar water.
$\ce{KI}$ which is a polar, ionic compound, will ionize and dissolve in water. When $\ce{KI}$ dissolves in water, it ionizes to $\ce{K+}$ and $\ce{I-}$.
The $\ce{I−}$ will react with $\ce{I2}$ to form the complex ion $\ce{I3-}$. $\ce{I3-}$ being negatively charged will dissolve in water.
