Question

The colour of iodine solution is discharged by shaking it with aqueous solution of:
A) Sodium sulphide
B) Sulphuric acid
C) Sodium sulphate
D) Sodium thiosulphate

Answer 1

Hint Firstly we should be clear what exactly is the iodine solution that is given in the problem statement. Now we know that it would show colour on the reaction of shaking when it is shaken in the presence of the Sodium thiosulphate which is the chemical compound of formula $N{a_2}{S_2}{O_3}$ .

Complete step by step answer:
Firstly we should be aware that the question is regarding colour showing nature of the iodine solution.
Now we have to apply a specific step by step approach towards finding the chemical reaction of the obtained product and the reactants and the compounds involved.
In the given question we know that the Iodine solution is discharged. Now this is done by shaking it with aqueous solution of sodium compound of Sodium thiosulphate.
The reaction which shows the chemistry behind the phenomenon is this:
$2N{a_2}{S_2}{O_3} + {I_2} \to N{a_2}{S_4}{O_6} + 2NaI$
Here $N{a_2}{S_4}{O_6}$ is a compound which is formed as the result. The proper chemical name of this compound is sodium tetrathionate.
Apart from that we also know that the compound of $NaI$ is also colourless and thus the given colour can’t be due to it.
Therefore, option (D) is correct.

Note: Sodium thiosulfate is used in gold mining, water treatment, analytical chemistry, the development of silver-based photographic film and prints, and medicine. The medical uses of sodium thiosulfate include treatment of cyanide poisoning and pityriasis. It is on the World Health Organization's List of Essential Medicines, the safest and most effective medicines needed in a health system.