In aqueous solution, \(Cr_2O_7^{2-}\) ion converts to which of the following in alkaline medium?
Show Hint
- \(Cr^{3+}\)
- \(CrO_4^{2-}\)
- \(CrO\)
- \(CrO_3\)
The Correct Option is B
Solution and Explanation
Chromate and dichromate ions exist in equilibrium depending upon the pH of the medium. In acidic medium, chromate ion changes to dichromate ion. In alkaline medium, dichromate ion changes to chromate ion.
Step 1: Write dichromate-chromate equilibrium.
The equilibrium is: \[ Cr_2O_7^{2-}+2OH^- \rightarrow 2CrO_4^{2-}+H_2O \]
Step 2: Understand colour and medium.
Dichromate ion is orange. \[ Cr_2O_7^{2-} \Rightarrow \text{orange} \] Chromate ion is yellow. \[ CrO_4^{2-} \Rightarrow \text{yellow} \] In alkaline medium, dichromate converts into chromate.
Step 3: Final answer.
Therefore: \[ Cr_2O_7^{2-} \xrightarrow{\text{alkaline medium}} CrO_4^{2-} \] Hence: \[ \boxed{\text{(B) }CrO_4^{2-}} \]
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