Question

Carbon and hydrogen are estimated by: (a) Leibig method (b) Duma's method (c) Carius method (d) Kjeldahl's method

Short answer

(a) Leibig method is used for estimating carbon and hydrogen.

Step-by-step solution

Understanding the Methods

Let's break down the options to identify which methods are used for estimating the presence of carbon and hydrogen in a compound. - The **Leibig Method** is used for determining carbon and hydrogen in organic compounds. - The **Duma's Method** is also used mainly for nitrogen estimation but can determine carbon when adapted for specific contexts. - The **Carius Method** is typically used to determine halogens, sulfur, and phosphorous, not directly for carbon or hydrogen. - The **Kjeldahl’s Method** is used for estimating nitrogen content, not directly for carbon or hydrogen.

Elimination of Unsuitable Methods

After analyzing the options, eliminate the methods not used or typically unsuitable for estimating carbon and hydrogen. - Remove **Carius Method** as it is used for halogens, sulfur, and phosphorous. - Remove **Kjeldahl's Method** as it is used for nitrogen. This leaves us with **Leibig Method** and **Duma's Method**.

Choosing the Correct Method

Among the remaining methods (**Leibig Method** and **Duma's Method**), identify the most specific method for carbon and hydrogen. Since Leibig Method is prominently used for carbon and hydrogen estimation as part of its primary function, it is considered the most appropriate choice.

Key concepts

Leibig Method

The Leibig Method is one of the earliest methods developed for estimating the presence of carbon and hydrogen in organic compounds. This is a classic approach in organic chemistry, often used in labs for elemental analysis. The process involves burning a known quantity of the organic compound in the presence of oxygen. The combustion of the compound produces carbon dioxide (\( CO_2 \)) and water (\( H_2O \)) as by-products.
The formed \( CO_2 \) is absorbed by a potassium hydroxide (\( KOH \)) solution leading to an increase in its weight. Similarly, \( H_2O \) is absorbed by concentrated sulfuric acid (\( H_2SO_4 \)), which also becomes heavier.
Here's how it works:

• Weigh a precise amount of the compound.
• Burn it in a combustion tube in the presence of oxygen.
• Absorb the \( CO_2 \) and \( H_2O \) formed in suitable absorbents (like \( KOH \) and \( H_2SO_4 \)).
• Measure the increase in weight of the absorbents to calculate the amounts of carbon and hydrogen.

This method is advantageous due to its direct and accurate results in determining carbon and hydrogen. Furthermore, since it involves the transformation of all the carbon and hydrogen into \( CO_2 \) and \( H_2O \), the measurements are quite reliable.

Duma's Method

The Duma's Method is traditionally known for nitrogen estimation but can also be adapted to estimate carbon. This technique involves passing the organic compound through red-hot copper oxide in a combustion tube. During this process, nitrogen is liberated and measured, but carbon and hydrogen can also be gauged.For carbon and hydrogen estimation, this method includes:

• The organic substance is burnt in an excess of oxygen.
• The resulting gases include \( CO_2 \), \( H_2O \), and nitrogen which can be captured and measured.
• \( CO_2 \) is absorbed over potassium hydroxide solution, while water is captured using magnesium perchlorate.

While Duma's Method is often reserved primarily for nitrogen, its versatility makes it suitable for broader elemental analysis with slight modifications. It's efficient and can provide accurate readings under the right conditions, especially when specific variations needed for carbon detection are employed.

Organic Chemistry Methods

In the realm of organic chemistry, methods for determining the elemental composition of compounds are crucial for understanding their structures and functions. Techniques like the Leibig and Duma's methods serve foundational roles in the analysis of organic materials. Here's why these methods are essential:

• They allow for precise determination of elemental content, which is pivotal in chemical synthesis and identifying unknown compounds.
• By understanding the proportion of carbon, hydrogen, and other elements, chemists can draw conclusions about molecular structures and possible reactions.
• Quantitative analysis of elements helps in quality control, ensuring the purity and concentration of compounds in various industries such as pharmaceuticals and environmental science.

The use of these methods provides a basis for more advanced techniques, paving the way for innovations in analytical chemistry. They highlight the interplay between theoretical principles and practical applications, showcasing how foundational concepts shape everyday scientific processes.