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Starch paper moistened with KI solution ...

Starch paper moistened with KI solution turns blue in ozone because of

A

Iodine liberation

B

Oxygen liberation

C

Alkali formation

D

Ozone is acidic

Text Solution

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The correct Answer is:
To solve the question regarding why starch paper moistened with potassium iodide (KI) solution turns blue in the presence of ozone (O3), we can follow these steps: ### Step-by-Step Solution: 1. **Understanding the Reaction**: - When potassium iodide (KI) is exposed to ozone (O3) in the presence of water (H2O), a chemical reaction occurs. The reaction can be represented as: \[ 2KI + O3 + H2O \rightarrow I2 + 2KOH + O2 \] 2. **Identifying the Products**: - The products of this reaction include iodine (I2), potassium hydroxide (KOH), and oxygen (O2). 3. **Oxidation Process**: - In this reaction, the iodide ion (I-) from potassium iodide is oxidized to iodine (I2). The oxidation state of iodine changes from -1 in KI to 0 in I2, indicating that oxidation has occurred. 4. **Role of Ozone**: - Ozone (O3) acts as a strong oxidizing agent. It facilitates the oxidation of iodide ions to iodine. This is crucial because the liberation of iodine is what causes the blue color in the starch paper. 5. **Starch-Iodine Complex Formation**: - The liberated iodine (I2) interacts with the starch present on the paper, forming a blue-colored complex. This is a well-known reaction where iodine forms a complex with starch, resulting in a characteristic blue color. 6. **Conclusion**: - Therefore, the reason why starch paper moistened with KI solution turns blue in the presence of ozone is due to the liberation of iodine (I2) as a result of the oxidation of iodide ions by ozone. ### Final Answer: The correct answer is that starch paper moistened with KI solution turns blue in ozone because of **iodine liberation**.
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