p-Amino-N,N-dimethylaniline is added to a strongly acidic solution of X. The resulting solution is treated with a few drops of aqueous solution of Y to yield blue colouration due to the formation of methylene blue. Treatment of aqueous solution of Y with reagent potassium hexacyanoferrate (II) leads to the formation of an intense blue precipitate. The precipitate dissolves on excess addition of the reagent. Similarly, the treatment of the solution of Y with the solution of potassium hexacyanoferrate (III) leads to a brown colouration due to the formation of Z.
Q. Compound X is

Options

A. `NaNO_3`
B. `NaCl`
C. `Na_2SO_4`
D. `Na_2S`

Answer

D

Explanation

X is `Na_2S` .
`Na_2S+2H^(o+)toH_2S+Na^(o+)`