Which one of the following set of elements can be detected using sodium fusion extract ?
(a) Sulphur

Q: Why do we use sodium metal specifically for this fusion?

Sodium is highly reactive and has a strong affinity for non-metals. It effectively breaks the strong covalent bonds in the organic compound and converts the extra elements into highly soluble ionic salts, which are perfect for aqueous chemical tests.

Q: Can we detect oxygen using Lassaigne's test?

No, oxygen cannot be detected using this test. Oxygen is usually identified by testing for specific oxygen-containing functional groups (like -OH, -CHO, -COOH) using other specific reagents.

Q: What happens if both nitrogen and sulphur are present in the compound?

If both are present in sufficient quantities, they combine with carbon and sodium to form sodium thiocyanate ($\text{NaSCN}$), which gives a blood-red coloration when treated with Iron(III) ions.

Q: Why do we plunge the red-hot fusion tube into distilled water?

Plunging the hot tube into water shatters the glass and safely dissolves the newly formed ionic sodium salts (like $\text{NaCN}$, $\text{Na}_2\text{S}$) into the water, creating the aqueous 'Sodium Fusion Extract' needed for further testing.

Q: Why is it necessary to boil the extract before performing the tests?

Boiling the extract helps to decompose any unreacted sodium metal (which reacts with water to form $\text{NaOH}$ and hydrogen gas) and ensures all the ionic salts are fully dissolved in the solution.

Question

Which one of the following set of elements can be detected using sodium fusion extract ?

Options:

(A) Sulphur, nitrogen, phosphorus, halogens

(B) Phosphorus, oxygen, nitrogen, halogens

(C) Nitrogen, phosphorus, carbon, sulphur

(D) Halogens, nitrogen, oxygen, sulphur

Sigma Percentile · Accepted Answer

### The Magic of Lassaigne's Test

Imagine you are a detective trying to find out what hidden elements are lurking inside an unknown organic compound. Organic compounds are primarily made of carbon and hydrogen, but they often contain 'extra' elements like nitrogen, sulphur, halogens, and phosphorus. The problem? These elements are tightly bound by strong covalent bonds.

To detect them using standard inorganic qualitative analysis, we must first break these covalent bonds and convert the elements into free, reactive ions. This is exactly where **Lassaigne's Test** (or the Sodium Fusion Test) comes to the rescue!

### Why Sodium?

Sodium is a highly reactive alkali metal. When we fuse the organic compound with a small piece of sodium metal at high temperatures, the intense heat and the reactive nature of sodium completely shatter the organic framework. The covalent bonds are broken, and the extra elements combine with sodium to form stable, water-soluble ionic salts.

Let's look at the specific chemical transformations that occur during this fiery fusion process:

**1. Nitrogen:**
If the compound contains nitrogen along with carbon, they react with sodium to form sodium cyanide.

$$	ext{Na} + 	ext{C} + 	ext{N} \xrightarrow{\Delta} 	ext{NaCN}$$

**2. Sulphur:**
If sulphur is present, it directly combines with sodium to form sodium sulphide.

$$2	ext{Na} + 	ext{S} \xrightarrow{\Delta} 	ext{Na}_2	ext{S}$$

**3. Halogens:**
Halogens (represented as X, which can be Cl, Br, or I) react to form their respective sodium halides.

$$	ext{Na} + 	ext{X} \xrightarrow{\Delta} 	ext{NaX}$$

**4. Phosphorus:**
Phosphorus is a bit special. During fusion, especially in the presence of an oxidizing agent like sodium peroxide, it gets converted into sodium phosphate.

$$3	ext{Na} + 	ext{PO}_4^{3-} \xrightarrow{\Delta} 	ext{Na}_3	ext{PO}_4$$

### The Final Verdict

Once the fusion is complete, the red-hot tube is plunged into distilled water, dissolving all these newly formed ionic salts. This resulting alkaline solution is called the **Sodium Fusion Extract**.

By performing specific chemical tests on this extract, we can easily confirm the presence of the cyanide, sulphide, halide, and phosphate ions. Notice that **oxygen** is conspicuously absent from this list. Oxygen is typically detected through specific functional group tests (like testing for alcohols, aldehydes, or carboxylic acids) rather than through Lassaigne's test.

Therefore, the correct set of elements that can be detected using the sodium fusion extract is **Sulphur, nitrogen, phosphorus, and halogens**.

Animated Solution for Chemistry - Organic Chemistry: Which one of the following set of elements can be detected using sodium fusion extract ?

Select Answer:

Visualized Solution

\text{Lassaigne's Test Principle}

\text{Detection of Nitrogen}

\text{Detection of Sulphur}

\text{Detection of Halogens}

\text{Detection of Phosphorus}

\text{Conclusion}

The Sigma Insight: Nomenclature and Characterisation

The Magic of Lassaigne's Test

Why Sodium?

The Final Verdict

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