See image — AITS & Test Series Chemistry Question

💡 Solution & Explanation

The colour of 2 HgI ,HgO 3 4 ,Pb O and   4 2 2 NH Cr O are red, red, red and orange spark respectively A, B and C all these are insoluble in water. But, all of these becomes soluble if some KI is added to water due to the formation very stable complex 2 4 HgI and 2 PbI . But, when the rad solid is heated in a test tube it cause the appearance of Hg metal on the cooler parts of the test tube which suggest that the red solid may be 2 HgI or, it may be HgO . But, on heating it produce violet fumes of 2I which suggest that the red solid is 2 HgI . The reaction are as follows:     Heat 2 2 4 2 2 HgI +2KI®K HgI solublein water HgI Hg+I Violet 