Problem 92
Question
In the detection of sulphur, sodium nitroprusside solution is added to the Lassaigne's test solution, a purple coloured is obtained. It is due to (a) \(\mathrm{Na}_{3}\left[\mathrm{Fe}(\mathrm{CN})_{5} \mathrm{NOSNa}\right]\) (b) \(\mathrm{Na}_{3}\left[\mathrm{Fe}(\mathrm{CN})_{6}\right]\) (c) \(\mathrm{Fe}(\mathrm{CNS})_{3}\) (d) \(\mathrm{Na}_{3}\left[\mathrm{Fe}(\mathrm{CN})_{5} \mathrm{NS}\right]\)
Step-by-Step Solution
Verified Answer
The correct answer is (d) \(\mathrm{Na}_{3}\left[\mathrm{Fe}(\mathrm{CN})_{5} \mathrm{NS}\right]\).
1Step 1: Understand the Reaction
The Lassaigne's test is used to detect the presence of certain elements in organic compounds. In this test, a sodium extract is prepared using sodium metal and then treated with different agents to test for the presence of specific elements such as nitrogen, sulphur, and halogens.
2Step 2: Identify the Role of Sodium Nitroprusside
Sodium nitroprusside is a sensitive reagent for sulphur detection. When it reacts with sulphide ions (\(\text{S}^{2-}\)) in the Lassaigne's test solution, it forms a purple complex, indicating the presence of sulphur.
3Step 3: Determine the Possible Products
Upon the addition of sodium nitroprusside, the interaction with sulphide ions yields a characteristic purple colored complex. We need to match this with one of the given options.
4Step 4: Analyze the Options
From the options, \(\mathrm{Na}_{3}\left[\mathrm{Fe}(\mathrm{CN})_{5} \mathrm{NOSNa}\right]\) (option a) indicates a complex with nitroprusside and sulphur, whereas \(\mathrm{Na}_{3}\left[\mathrm{Fe}(\mathrm{CN})_{5} \mathrm{NS}\right]\) (option d) specifically signifies a complex with sulphur linkage, leading to the purple colour.
5Step 5: Select the Correct Option
The purple color results from the formation of the complex \(\mathrm{Na}_{3}\left[\mathrm{Fe}(\mathrm{CN})_{5} \mathrm{NS}\right]\), which is option (d). This correctly represents the chemical reaction that occurs during the detection of sulphur using sodium nitroprusside.
Key Concepts
Sulphur DetectionSodium NitroprussideOrganic Analysis
Sulphur Detection
Sulphur detection is a significant part of understanding chemical compositions in organic chemistry. One of the effective methods for detecting sulphur is Lassaigne's test. In this test, organic compounds are fused with sodium, which breaks down the chemical bonds to form simpler substances. When sulphur is present in the compound, it gets converted to sodium sulphide (\( ext{Na}_2 ext{S} \)).
To confirm the presence of sulphur, the sodium extract is treated with sodium nitroprusside. If sulphides are present, a distinct purple color is observed, which confirms sulphur's presence. This color change is a clear indicator because it involves the formation of a complex ionic structure that is specific to sulphur ions.
This test is quite reliable for sulphur detection due to its precision and the unmistakable color change. However, care must be taken during the test to ensure no contamination and precise chemical mixing, as this could lead to false positives or negatives in results.
To confirm the presence of sulphur, the sodium extract is treated with sodium nitroprusside. If sulphides are present, a distinct purple color is observed, which confirms sulphur's presence. This color change is a clear indicator because it involves the formation of a complex ionic structure that is specific to sulphur ions.
This test is quite reliable for sulphur detection due to its precision and the unmistakable color change. However, care must be taken during the test to ensure no contamination and precise chemical mixing, as this could lead to false positives or negatives in results.
Sodium Nitroprusside
Sodium nitroprusside plays a crucial role in chemical analysis, especially in detecting sulphur. It is a complex compound known for its sensitive and specific reactions with sulphide ions present in a mixture. In the presence of sulphide ions (\( ext{S}^{2-} \)), sodium nitroprusside forms a purple-colored complex.
This reagent is valuable because it reacts selectively with sulphide ions rather than with other common ions like nitrates or chlorides. The result is a powerful visual indicator that can be observed with the naked eye. This sensitivity makes it an invaluable tool in qualitative analysis, particularly within laboratory settings for organic chemistry.
The use of sodium nitroprusside is not limited to sulphur detection. It finds application in various fields, including medicinal chemistry and even medical diagnostics. However, its primary utility in organic analysis remains the simple and definitive indication it provides in the presence of sulphur.
This reagent is valuable because it reacts selectively with sulphide ions rather than with other common ions like nitrates or chlorides. The result is a powerful visual indicator that can be observed with the naked eye. This sensitivity makes it an invaluable tool in qualitative analysis, particularly within laboratory settings for organic chemistry.
The use of sodium nitroprusside is not limited to sulphur detection. It finds application in various fields, including medicinal chemistry and even medical diagnostics. However, its primary utility in organic analysis remains the simple and definitive indication it provides in the presence of sulphur.
Organic Analysis
Organic analysis refers to the qualitative and quantitative examination of organic compounds to understand their composition and structure. It is a foundational aspect of organic chemistry, providing insights into the elements that make up a compound. Various tests, including Lassaigne's test, are used to identify elements like sulphur, nitrogen, and halogens in organic substances.
Through organic analysis, chemists can elucidate the presence of certain groups and predict the behavior of compounds in reactions. By conducting tests, chemists can construct a clearer picture of the compound's molecular structure. The tests like Lassaigne's test serve as a sandbox for identifying elements in unknown compounds, allowing chemists to form hypotheses about their composition.
In a nutshell, organic analysis is essential for anyone dealing with organic chemistry, as it lays the groundwork for understanding complex organic molecules, reactions, and the development of new compounds. The ability to identify elemental composition accurately ensures progress in research and practical applications across different scientific fields.
Through organic analysis, chemists can elucidate the presence of certain groups and predict the behavior of compounds in reactions. By conducting tests, chemists can construct a clearer picture of the compound's molecular structure. The tests like Lassaigne's test serve as a sandbox for identifying elements in unknown compounds, allowing chemists to form hypotheses about their composition.
In a nutshell, organic analysis is essential for anyone dealing with organic chemistry, as it lays the groundwork for understanding complex organic molecules, reactions, and the development of new compounds. The ability to identify elemental composition accurately ensures progress in research and practical applications across different scientific fields.
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