Student Question

Does iodine dissolve in ethanol?


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Iodine, which has the form `I_2` , is soluble in ethanol. It doesn't dissolve as well in water because iodine is non-polar and water is very polar. Ethanol is polar, but less so than water.

Polar substances dissolve in other polar substances and non-polar substances dissolve in other non-polar substances. In order for a solute to dissolve in a solvent they must have similar intermolecular attractions. If the solvent-solvent attractions or solute-solute attractions are stronger than the solvent-solute attractions the solute won't dissolve well.

The solubility of iodine in alcohol is increased by adding some NaI. This facilitates the ionization of some of the `I_2`  as `I_2` and `I-`   form    `I_3^-` . This solution, called Tincture of Iodine, is used as a disinfectant.

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