Question:
The substance used to convert sodium chromate to sodium dichromate in one of the stages of preparation of potassium dichromate is
The substance used to convert sodium chromate to sodium dichromate in one of the stages of preparation of potassium dichromate is
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Remember the equilibrium:
Chromate (Yellow) \(\xrightarrow{H^+}\) Dichromate (Orange)
Dichromate (Orange) \(\xrightarrow{OH^-}\) Chromate (Yellow)
Chromate (Yellow) \(\xrightarrow{H^+}\) Dichromate (Orange)
Dichromate (Orange) \(\xrightarrow{OH^-}\) Chromate (Yellow)
Updated On: Apr 29, 2026
- \(H_2O_2\)
- \(KClO_3\)
- \(NaOH\)
- \(Na_2CO_3\)
- \(H_2SO_4\)
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The Correct Option is
Solution and Explanation
Step 1: Understanding the Concept:
Chromates and dichromates are interconvertible in aqueous solution depending on the pH.
Step 3: Detailed Explanation:
Sodium chromate (\(Na_2CrO_4\)) is yellow and is stable in alkaline medium.
To convert it to sodium dichromate (\(Na_2Cr_2O_7\)), which is orange, the solution must be acidified.
\[ 2Na_2CrO_4 + H_2SO_4 \to Na_2Cr_2O_7 + Na_2SO_4 + H_2O \]
This conversion is a key step in the industrial preparation of potassium dichromate.
Step 4: Final Answer:
Sulphuric acid (\(H_2SO_4\)) is used.
Chromates and dichromates are interconvertible in aqueous solution depending on the pH.
Step 3: Detailed Explanation:
Sodium chromate (\(Na_2CrO_4\)) is yellow and is stable in alkaline medium.
To convert it to sodium dichromate (\(Na_2Cr_2O_7\)), which is orange, the solution must be acidified.
\[ 2Na_2CrO_4 + H_2SO_4 \to Na_2Cr_2O_7 + Na_2SO_4 + H_2O \]
This conversion is a key step in the industrial preparation of potassium dichromate.
Step 4: Final Answer:
Sulphuric acid (\(H_2SO_4\)) is used.
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