Question

If $CO _2$ is passed into waste water containing $CrO _4^{2-}$ (yellow) then solution turns

• A. Green due to the formation of $Cr ^{3+}$
• B. Blue due to the formation of $CrO _5$
• C. Orange due to the formation of $Cr _2 O _7^{2-}$
• D. Black due to the formation of $Cr _2 O _3$

Answer 1

Answer: (C)

$CO _2+ H _2 O \rightleftharpoons H _2 CO _3 \rightleftharpoons 2 H ^{+}$
$\underset{\text{Yellow}}{2 CrO _4^{2-}}+ \underset{\text{orange}}{2 H ^{+}} \rightarrow H _2 O + Cr _2 O _7^{2-}$