Question

$KI$ when heated with conc. sulfuric acid gives
A. $HI$
B. ${{I}_{2}}$
C. $HI{{O}_{3}}$ ​
D. $KI{{O}_{3}}$

Answer 1

Hint: If we see the reactivity trend of halogens then iodine is least reactive. So, any strong oxidising agent like sulfuric acid can easily oxidise iodine from its salt.

Complete Step by Step Answer:
Concentrate sulfuric acid on reaction with iodine salt that is potassium iodide gives potassium bisulfate along with hydrogen iodide. This hydrogen iodide in reaction with concentrated sulfuric acid produces iodine gas which gives the violet colour along with water and sulphur dioxide gas.’

Thus the reaction is given as follows:
$KI+{{H}_{2}}S{{O}_{4}}\to KHS{{O}_{4}}+HI$
$2HI+{{H}_{2}}S{{O}_{4}}\to 2{{H}_{2}}O+{{I}_{2}}+SO{}_{2}$
Thus we can write that $KI$ when heated with conc. Sulfuric acid gives iodine gas.
Thus the correct option is B.

Additional Information: Iodine is a halogen element. It has the symbol of $I$. It generally exists as a gas. It has the colour of violet blue. Iodine is generally obtained from seaweed. Starch generally acts as an indicator in titration reactions to determine the end point of a titration. Iodine gas reacts with starch, an indicator gives blue colour.

Note: To get iodine gas in this reaction a minimum amount of sulfuric acid is used. This addition of excess sulfuric acid can slow the process and does not liberate the iodine gas.