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Question
Why is freshly prepared ferrous sulphate solution used for testing the nitrate radical in the brown ring test?
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Solution
We use freshly prepared ferrous sulphate solution because exposure to air, such as storing it in a reagent bottle, causes it to oxidise to ferric sulphate solution. The [NO] molecule will not form an additive compound with ferric sulphate; hence, the brown ring test will not be successful.
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