Cr+6 must be converted to Cr+3 before precipitation.

Cr+6 must be converted to Cr+3 before precipitation.

• A. False
• B. Partially true
• C. Cannot be determined
• D. True

Answer: (D)

Crodium in wastewater is removed by forming an insoluble solid, and that happens with Cr(III) as chromium hydroxide. Cr(VI) is highly soluble and stays in solution, so it won’t precipitate out on its own. To remove chromium by precipitation, Cr(VI) must first be reduced to Cr(III), then the pH is adjusted to encourage Cr(III) to form Cr(OH)3, which can precipitate and be settled out. This makes the statement true: conversion to Cr(III) is a required step before precipitation.

Crodium in wastewater is removed by forming an insoluble solid, and that happens with Cr(III) as chromium hydroxide. Cr(VI) is highly soluble and stays in solution, so it won’t precipitate out on its own. To remove chromium by precipitation, Cr(VI) must first be reduced to Cr(III), then the pH is adjusted to encourage Cr(III) to form Cr(OH)3, which can precipitate and be settled out. This makes the statement true: conversion to Cr(III) is a required step before precipitation.