A pollutant in drinking water from old pipes gives a yellow precipitate with potassium iodide, Pb^2+ + 2I^- -> PbI2, which dissolves in hot water and reappears as golden spangles on cooling. The pollutant and its principal harmful effect are:

lead; it inhibits haem synthesis and causes anaemia and damage to kidney and brain

cadmium; it causes itai-itai disease

nitrate; it causes blue baby syndrome

mercury; it causes Minamata disease

JEE Advanced levelSingle correct optionDifficulty 3 of 3ev150

A pollutant in drinking water from old pipes gives a yellow precipitate with potassium iodide, $Pb X^{2 +} + 2 I X^{-} PbI X_{2}$ , which dissolves in hot water and reappears as golden spangles on cooling. The pollutant and its principal harmful effect are:

Alead; it inhibits haem synthesis and causes anaemia and damage to kidney and brain
Bcadmium; it causes itai-itai disease
Cnitrate; it causes blue baby syndrome
Dmercury; it causes Minamata disease

Yellow

PbI X_{2}

that dissolves in hot water and recrystallises as golden spangles identifies

Pb X^{2 +}

. Lead interferes with haem synthesis and damages the kidney, liver and nervous system. The other diseases belong to other pollutants.