Q. 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
A) $\left( {NH}_{4} \right)_{2}{Cr}_{2}O_{7}$
B) ${HgI}_{2}$
C) $HgO$
D) ${Pb}_{3}O_{4}$
Explanation
(b)
${HgI}_{2} + 2KI \longrightarrow \ K_{2}{HgI}_{4}$
soluble
${HgI}_{2}\ \ \overset{\mathrm{\Delta}}{\rightarrow}Hg + I_{2}$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.