Question

Iodine solution is prepared by dissolving iodine in:
A. $NaOH$
B. $N{a_2}C{O_3}$
C. ${H_2}O$
D. $KI$

Answer 1

Iodine solution is also known as tincture of iodine, iodine tincture, or weak iodine solution. It is used in medicinal cases as an antiseptic. The polarity of the compound can be analyzed for the correct answer.

Complete step by step answer:
Iodine solution is 2-7 $\%$ elemental iodine, along with potassium iodide or sodium iodide, dissolved in a mixture of water and ethanol.
These are characterized by the presence of alcohol.
Iodine molecule is covalent and exists as a non-polar, diatomic molecule. This non-polar property is the reason for its non-dissolution in the water solvent.
$NaOH$ is the most polar compound of the options and thus it is soluble in water, but the iodine needed will not be able to get in the solution due to its non-polar nature in water.
The other option is sodium carbonate $N{a_2}C{O_3}$ . It contains the ionic bond and thus is not fit for the formation of iodine solution.
Since iodine exists as non-polar so it can’t be dissolved in water which is polar.
On considering the fourth option potassium iodide $KI$ , it is an ionic compound which upon dissolution will give iodide ions which may react with the iodine to form the required solution.

So, the correct answer is Option D.

Note: We know that Polar compounds dissolve in polar solvents and vice-versa.Upon dissolution, with water, only $KI$ gives iodide ions for the formation of iodine solution. We can also $NaI$ can also be used in place of $KI$ .