Question

This section contains multiple choice questions. Each question has 4 choices (a), (b), (c) and (d), out of which ONLY ONE is correct. Lassaigne's solution gives violet colouration with sodium nitroprusside. This indicates presence of (a) nitrogen (b) fluorine (c) chlorine (d) sulphur

Short answer

Answer: (d) sulphur

Step-by-step solution

Understanding the Lassaigne's Test

Lassaigne's Test is a simple qualitative test performed to detect the presence of nitrogen, halogens, and sulfur in an organic compound. In this test, the organic compound is heated with sodium metal, and the resulting solution is called Lassaigne's solution, which is then reacted with various reagents to check for the presence of the mentioned elements.

Understanding the reaction with sodium nitroprusside

Sodium nitroprusside reacts with some specific elements to give different coloration. This property can be used to detect the elements present in the test solution. When Lassaigne's solution reacts with sodium nitroprusside and shows a violet colour, it indicates the presence of sulfur. It is important to note that nitrogen, fluorine, and chlorine do not exhibit this colour change with sodium nitroprusside.

Identify the correct option

Given the above information, we can now identify the correct option among the given choices. As we have found that sulfur is the element that gives the violet coloration with sodium nitroprusside in Lassaigne's Test, the correct answer is: (d) sulphur

Key concepts

Qualitative Analysis in Chemistry

Qualitative analysis is an essential part of chemistry that focuses on identifying the components of a chemical substance. Unlike quantitative analysis, which measures the amount or concentration of elements, qualitative analysis seeks to determine the presence or absence of different substances.
This form of analysis is particularly valuable in organic chemistry for identifying functional groups and various elements within a compound.

Some techniques used in qualitative analysis include:

• Color tests, where a change in color indicates the presence of a particular element or compound.
• Precipitation reactions, where forming a solid substance from the reaction helps indicate specific ions.
• Flame tests, which identify elements based on flame color emissions.

Qualitative analysis provides insightful information, allowing chemists to understand the basic composition of complex substances quickly. Its simplicity and practicality make it a favorite among chemists for initial investigations.

Exploring Organic Chemistry

Organic chemistry is a fascinating branch of chemistry that studies carbon-containing compounds, particularly those with carbon-carbon bonds. This field is highly diverse, encompassing everything from small molecules like methane to large complex structures like proteins and DNA.

Within organic chemistry, understanding the composition and structure of compounds is critical. Various analytical tools and tests, like Lassaigne's Test, are used to detect different elements within organic compounds. This analysis is crucial for:

• Determining compound purity.
• Understanding chemical reactions.
• Synthesizing new materials.

Organic chemistry plays a vital role in many industries including pharmaceuticals, agrochemicals, and petrochemicals. The study of organic chemistry is like a gateway to understanding how molecules interact in biological or synthetic environments, leading to innovations that improve daily life.

Element Detection Techniques

Element detection refers to the methods used to identify which elements are present in a chemical compound. Techniques like Lassaigne’s Test are simple yet powerful approaches in organic chemistry for recognizing specific elements such as nitrogen, halogens, and sulfur.

Here's how Lassaigne's Test works:

• The organic substance is fused with sodium, creating a solution that contains the elements turned into soluble ionic forms.
• This resulting Lassaigne’s solution is then treated with various reagents to observe specific reactions.
• Sodium nitroprusside, for instance, produces a violet coloration when sulfur is present.

These distinct reactions allow chemists to determine the presence of specific elements quickly. Element detection is critical for verifying compound structures and ensuring the safety and efficacy of chemical products. Through these simple tests, chemists can gather initial data before moving on to more detailed quantitative analyses.