Question

A purple coloured non-metal forms a brown solution in alcohol which is applied on wounds as an antiseptic. The non-metal is:
[A] Iodine
[B] Bromine
[C] Chlorine
[D] Sulphur

Answer 1

Hint: The correct answer here is a group 17 element. Its atomic number is 53. It is the most electropositive halogen. Halogens react differently with different alcohols but the correct answer here along with ethanol, water and sodium iodide makes an antiseptic solution.

Complete Step by Step Solution: Before answering this question, let us see the reaction of the halogens given and sulphur with alcohol.
First we have iodine. When we dissolve 2-7% elemental iodine with potassium or sodium iodide in a mixture of iodine and water, we get a brown solution which is characterised by the presence of alcohol and can be applied on wounds as antiseptic. Therefore, this can be the correct answer.
Then we have bromine. Bromine in reaction with alcohol leads to the oxidation of alcohol and then forms a carboxylic acid with hydrogen bromide. We can write the reaction as-
\[\begin{align}
& {{C}_{2}}{{H}_{5}}OH+B{{r}_{2}}\to C{{H}_{3}}CHO+2HBr \\
& C{{H}_{3}}CHO+B{{r}_{2}}+{{H}_{2}}O\to C{{H}_{3}}COOH+2HBr \\
\end{align}\]
Thus the solution is not used as an antiseptic and it is not the correct answer.
Now let us discuss chlorine. When we add chlorine to ethyl alcohol in presence of potassium hydroxide, we get chloroform. We can write the reaction as-
$\begin{align}
& C{{l}_{2}}+C{{H}_{3}}C{{H}_{2}}OH\to C{{H}_{3}}CHO+2HCl\text{ }\left[ oxidation \right] \\
& CC{{l}_{3}}CHO+KOH\xrightarrow{hydrolysis}CHC{{l}_{3}}+HCOOK \\
\end{align}$
This is not a brown coloured solution as chloroform is colourless and is not used as an antiseptic. Therefore, this is not the correct option either.
And lastly, we have sulphur. When we heat ethanol with concentrated sulphuric acid at a very high temperature, we get ethene and a molecule of water. We can write the reaction as-
\[{{C}_{2}}{{H}_{5}}OH+{{H}_{2}}S{{O}_{4}}(conc.)\to C{{H}_{2}}=C{{H}_{2}}+{{H}_{2}}O\]
This is also not a brown colour solution and neither is ethene used as an antiseptic. Therefore this is not the correct answer either.
As we can see from the above discussion that iodine forms a brown colour solution with alcohol which can be applied on wounds as it acts as an antiseptic.

Therefore, the correct answer is option [A] iodine.

Note: The mixture of 2-7% iodine with sodium iodide of potassium iodide with ethanol and water is known as tincture of iodine. It is used to disinfect wounds and also to sanitize water for drinking. This protects against bacteria and viruses but not against protozoa. Iodine solution is used to sanitize the surface of fruits and vegetables too but it is not considered safe to eat raw after sanitizing them with iodine.