Question

When Sulphur is boiled with $N{a_2}S{O_3}$ solution, the compound formed is:
A.Sodium sulphide
B.Sodium sulphate
C.Sodium persulphate
D.Sodium thiosulphate

Answer 1

Hint: When Sulphur is boiled with $N{a_2}S{O_3}$ , a compound is produced with excess of $AgN{O_3}$ solution, and a compound is formed which is soluble in water.

Complete step by step answer:
When Sulphur is boiled with $N{a_2}{S_2}{O_3}$ solution, the compound formed is sodium thiosulphate.
The reaction is as shown,
 $8N{a_2}{S_2}{O_3} + S \to 8N{a_2}{S_2}{O_3}$
Sodium thiosulphate is an inorganic compound. Typically it is available as the white or colorless pentahydrate, $N{a_2}{S_2}{O_3}.5{H_2}O$ .
The solid is an efflorescent crystalline substance that dissolves well in water.
It is a reducing agent and is often used to control the reductive-oxidative properties of the sulphide mineral surface during floatation. It is used to reduce iodine back to iodide before iodine can complex with the starch to form the characteristic blue-black color.

Hence, option D is correct.

Additional information:
Thiosulphate ion is a moderately strong reducing agent used by an indirect procedure in which iodine acts as an intermediate to determine the various oxidizing agents. Starch, irreversibly decomposes in solutions containing high levels of iodine. Thus, it is evident that sodium thiosulphate is a very important chemical compound in our lives.

Note:
Sodium thiosulphate is an inorganic sodium salt composed of sodium and thiosulphate ions in a $2:1$ ratio. It has a role as an antidote to cyanide poisoning, a nephroprotective agent and an antifungal drug. It is used in swimming pools as a reagent in testing of pool water, primarily to neutralize the whitening effect of chlorine present in a water sample.