Question

During formation of sodium extract, generally the substance that ignites is: (a) \(\mathrm{Na}\) (b) \(\mathrm{O}_{2}\) (c) \(\mathrm{CO}_{2}\) (d) \(\mathrm{H}_{2}\)

Short answer

(a) Na (sodium) usually ignites.

Step-by-step solution

Understand the context of sodium extract formation

In the preparation of sodium extract, a piece of dry sodium is added to an organic compound to help in the detection of certain elements like nitrogen, sulfur, and halogens through a series of chemical reactions. This process is known as 'Lassaigne's test'.

Know the properties of sodium

Sodium is a highly reactive metal, especially when exposed to air or water. When sodium is exposed to moisture in the air, it can react vigorously, sometimes to the point of igniting, due to the formation of sodium oxide and/or sodium hydroxide.

Analyze potential substances that could ignite

In the given options: (a) Sodium (\(\mathrm{Na}\)) can react exothermically with moisture, (b) Oxygen (\(\mathrm{O}_2\)) is essential for ignition but is not itself the substance that typically ignites in this context, (c) Carbon dioxide (\(\mathrm{CO}_2\)) is a fire extinguisher component and non-combustible, and (d) Hydrogen (\(\mathrm{H}_2\)) may ignite but is not directly part of the sodium solution formation.

Identify the substance that ignites

Considering the above facts, the substance that usually catches fire during the preparation of sodium extract in this context is sodium (\(\mathrm{Na}\)), due to its high reactivity, especially in contact with moisture.

Key concepts

Lassaigne's Test

Lassaigne's test is a classical analytical procedure used to detect the presence of elements like nitrogen, sulfur, and halogens in organic compounds. This technique involves heating the organic material with a small piece of metallic sodium. The high temperatures facilitate the fusion of the elements in the organic compound with sodium, forming sodium salts. These salts are more water-soluble and thus easier to test for the presence of specific elements.

The process begins with preparing a sodium extract, also known as a sodium fusion extract. The extract forms when sodium fuses with the organic compound, thus "trapping" potential non-metals from the compound in the form of water-soluble salts. These salts are then tested further to detect specific ions, which indicate the presence of the elements originally in the organic sample.

The procedure is essential in identifying the building blocks of organic compounds, providing crucial insights into their chemical structure. It's widely used due to its effectiveness and the relatively straightforward laboratory process involved.

Sodium Properties

Sodium is an alkali metal found in Group 1 of the periodic table. It's renowned for its high reactivity, particularly with water and air. Because of its strong oxidizing abilities, sodium must be stored in a manner that prevents contact with moisture, often submerged in oil or sealed in airtight conditions.

When sodium contacts moist air, it reacts to form sodium hydroxide and hydrogen gas. This reaction can be vigorous and exothermic, leading to the ignition of hydrogen if the conditions are suitable. Sodium's properties include:

• Highly reactive nature.
• Softeness and light weight, allowing easy cutting with a knife.
• Silvery-white appearance, although it tarnishes quickly when exposed to air due to the formation of a sodium oxide layer.
• Low melting point for a metal, melting at about 98°C.

Due to these properties, sodium is both challenging and fascinating to work with in laboratory settings, especially during procedures like Lassaigne's test.

Organic Compound Analysis

Organic compound analysis is a foundational aspect of chemistry, exploring the composition of carbon-containing compounds. This analysis aids in identifying the types of atoms that constitute a compound, clarifying its molecular framework.

In the context of Lassaigne's test, organic compound analysis involves breaking down the compound with sodium to create a simpler system for detecting non-metal elements such as nitrogen, sulfur, and halogens. The key steps include:

• Fusion of the organic compound with sodium to produce water-soluble salts.
• Extracting these salts with water to form a sodium fusion extract.
• Performing tests on this extract to reveal the presence of specific ions.

The tests are particular for each element: for instance, testing for nitrogen involves the formation of cyanide salts that react with iron to form Prussian blue.

Overall, this analysis not only helps to identify elements but also provides insights into the potential functionalities and reactivity of the organic molecules, thus deepening our understanding of organic chemistry.