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A red solide is insoluble in water. Howe...

A red solide is insoluble in water. However it becomes soluble if some KI is added to water. On heating the red solid in a test tube, there is liberation of some violet coloured fumes and droplets of a metal appear on the cooler parts of the test tube. The red solid is :

A

`HgO`

B

`Pb_(3)O_(4)`

C

`(NH_(4))_(2) Cr_(2)O_(7)`

D

`Hgl_(2)`

Text Solution

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The correct Answer is:
To solve the question, we need to analyze the properties and reactions of the red solid described. Here’s a step-by-step breakdown of the solution: ### Step 1: Identify the Red Solid The question states that the red solid is insoluble in water but becomes soluble when potassium iodide (KI) is added. We need to consider compounds that are red and have this property. **Hint:** Look for red solids that are known to react with potassium iodide. ### Step 2: Consider Possible Compounds From the video transcript, we learn that HgI2 (mercury(II) iodide) is a red solid. Other candidates like Pb3O4 (lead(II,IV) oxide) and others were eliminated because they do not match the described properties. **Hint:** Focus on the solubility behavior of the compounds with KI. ### Step 3: Reaction with KI When KI is added to HgI2, it forms a soluble complex known as Nessler's reagent. This indicates that HgI2 is indeed the red solid we are looking for. **Hint:** Understand the significance of the reaction between KI and the red solid. ### Step 4: Heating the Red Solid Upon heating HgI2, it decomposes to produce mercury (Hg) and iodine (I2). The liberation of violet-colored fumes is due to the formation of iodine gas. **Hint:** Remember that heating can lead to decomposition reactions, which may produce gases. ### Step 5: Observing the Metal Droplets The appearance of droplets of metal on the cooler parts of the test tube indicates that mercury is being produced as a result of the decomposition of HgI2. **Hint:** Consider the physical state of the products formed during the reaction. ### Conclusion Based on the analysis, the red solid described in the question is **HgI2 (mercury(II) iodide)**. ### Final Answer The red solid is **HgI2 (mercury(II) iodide)**. ---
To solve the question, we need to analyze the properties and reactions of the red solid described. Here’s a step-by-step breakdown of the solution: ### Step 1: Identify the Red Solid The question states that the red solid is insoluble in water but becomes soluble when potassium iodide (KI) is added. We need to consider compounds that are red and have this property. **Hint:** Look for red solids that are known to react with potassium iodide. ### Step 2: Consider Possible Compounds ...
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