Question

A certain compound X when treated with copper sulphate solution yields a brown precipitate. On adding hypo solution, the precipitate turns white. The compoundXis

• A. $K_2CO_3$
• B. KI
• C. KBr
• D. $K_3PO_4$

Answer 1

Answer: (B)

KI

Answer 2

When potassium iodide is reacted with CuS04,
it gives iodine gas which is brown colour. This
iodine react with sodium thiosulphate and form
white precipitate of sodium tetrathionate.
$2CuSO_4 \, + \, 4 KI \, \longrightarrow \, K_2 SO_4 \, + \, I_2 \, + 2CuI$
$2Na_2S_2O_3 \, + \, I_2 \, \longrightarrow \, Na_2S_4O_6 \, + \, 2NaI$