D-And F-Block Elements Ques 482

Question: A red solid is insoluble in water. However it becomes soluble if some KI is added to water. Heating the red solid in a test tube results in liberation of some violet coloured fumes and droplets of a metal appear on the cooler parts of the test tube. The red solid is

Options:

A) $ HgI_2 $

B) $ HgO $

C) $ Pb_3O_4 $

D) $ {{(NH_4)}_2}Cr_2O_7 $

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Answer:

Correct Answer: A

Solution:

When KI is added to mercuric iodide it disssolve in it and form complex. $ \underset{\begin{smallmatrix} red,,solid \\ (insoluble) \end{smallmatrix}}{\mathop{HgI_2}},+KI\to \underset{(soluble)}{\mathop{K_2[HgI_4]}}, $ On heating $ HgI_2 $ decomposes as $ HgI_2\rightarrow Hg+\underset{( violetvapours )}{\mathop{I_2}}, $



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