Question

Salt R is black in colour. On reacting with conc. HCl, it liberates a pungent greenish yellow gas which turns moist starch iodide paper blue black. Identify the salt.

Answer 1

I also gave chemistry paper today

i have written manganese dioxide....

Answer 2

Answer:

Because, the evolved gas is pungent and greenish yellow in colour, this confirms that the gas is chlorine gas as it also turns the moist starch iodide paper blue.

Now,

When this salt reacts with concentrated Hydrochloric acid, and that the salt is also black in colour, so it definitely has to be Manganese Dioxide. (MnO2)

Hope this helps you !