A red colouration or precipitate is not obtained when:

Options

A. `Fe^(3+)` reacts with potassium thiocyanate
B. `Fe^(2+)` reacts with dimethylglyoxime.
C. `Hg^(2+)` reacts with potassium iodide.
D. None

Answer

D

Explanation

(A)`Fe^(3+)+3SCN^(-)toFe(SCN)_(3)`(red solution)
(B)Red solution of iron `(II)` dimethylglyoxime.
(C )`Hg^(2-)+2l^(-)toHgl_(2) darr` (red).