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Following tests are shown by (i) Decol...

Following tests are shown by
(i) Decolourisation of acidified soln. of `KMnO_4`
(ii) Liberation of `I_2` from an acidified soln. of `K I`
(iii) On treatment with dil `HCl`, brown fumes of `NO_2` which turns `FeSO_4` soln. black.

A

Nitrites

B

Nitrates

C

Both `(a)` and `(b)`

D

Neither (a) nor (b)

Text Solution

AI Generated Solution

The correct Answer is:
To solve the question regarding the tests shown by certain compounds, we will analyze each test step by step and determine which compound (nitrites or nitrates) can give the observed results. ### Step 1: Analyze the first test - Decolorization of acidified solution of KMnO4 - **Explanation**: KMnO4 (potassium permanganate) is a strong oxidizing agent. When it is reduced, it changes from purple to colorless, indicating a reduction reaction. - **Conclusion**: For decolorization to occur, the compound must act as a reducing agent. ### Step 2: Analyze the second test - Liberation of I2 from an acidified solution of KI - **Explanation**: In this reaction, potassium iodide (KI) contains iodide ions (I⁻). When oxidized, iodide ions convert to iodine (I2), which is a change from -1 oxidation state to 0 oxidation state. - **Conclusion**: This indicates that the compound must be capable of acting as an oxidizing agent. ### Step 3: Analyze the third test - Brown fumes of NO2 from treatment with dilute HCl - **Explanation**: When nitrites (NO2⁻) react with dilute HCl, they produce nitrogen dioxide (NO2), which is a brown gas. This gas can react with FeSO4 (iron(II) sulfate) to form iron(III) sulfate, which can turn the solution black due to the formation of iron(III) compounds. - **Conclusion**: This suggests that the compound must be capable of producing NO2 gas. ### Step 4: Determine the compound - **Nitrites (NO2⁻)**: - Can reduce KMnO4 (first test). - Can oxidize I⁻ to I2 (second test). - Can produce NO2 gas when treated with HCl (third test). - **Nitrates (NO3⁻)**: - Cannot reduce KMnO4 (as they are in the highest oxidation state of +5). - Cannot liberate I2 from KI (as they cannot act as a reducing agent). - Can produce NO2 gas, but they do not fulfill the first two tests. ### Final Conclusion - The only compound that can fulfill all three tests is **nitrites**. Therefore, the correct answer is **Option 1: Nitrites**. ---
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