Problem 47 - A Complete Resource Book in Chemistry for JEE Main

Question

In Kjeldahl's method, \(\mathrm{CuSO}_{4}\) acts as (a) reducing agent (b) oxidizing agent (c) catalytic agent (d) hydrolyzing agent

Step-by-Step Solution

Answer

(c) catalytic agent

Step 1: Understanding Kjeldahl's Method

In Kjeldahl's method, the purpose is to determine the nitrogen content in a compound by converting nitrogen into ammonia, which is then measured. This involves digesting the sample with sulfuric acid, often using catalysts to accelerate the reaction.

Step 2: Role of Catalysts

In Kjeldahl's method, certain substances are added to act as catalysts, which enhance the breakdown of the organic nitrogen compounds into simpler substances that eventually convert into ammonium sulfate.

Step 3: Identify the Role of  extrm{CuSO}_{4}

Copper sulfate,  extrm{CuSO}_{4}, serves as a catalyst in the Kjeldahl digestion process. As a catalytic agent, it speeds up the reaction without being consumed, making the conversion of nitrogen more efficient.

Key Concepts

Understanding Catalytic Agents in Chemistry

Catalytic agents play a vital role in chemistry by increasing the rate of chemical reactions without undergoing permanent change themselves. This means that a catalyst can be repeatedly used to accelerate reactions without being consumed in the process.
Catalysts lower the activation energy required for reactions to occur. This is particularly beneficial in enhancing the efficiency of industrial processes and laboratory reactions.

In the context of Kjeldahl's method, a catalyst is critical as the reaction of breaking down nitrogen compounds into simpler ammonium forms needs to happen quickly and effectively, primarily when dealing with complex organic materials. Catalysts facilitate this breakdown by adjusting pathways or forming temporary intermediate states with the reactants, easing the transition to the final products.

• They increase the reaction rate without being consumed.
• They work by reducing the activation energy needed for a reaction.
• In Kjeldahl's method, they help in the rapid breakdown of nitrogen into ammonia.

Nitrogen Determination Using Kjeldahl's Method

Nitrogen determination is essential in analyzing proteins and other nitrogen-containing compounds. Kjeldahl's method is a classic approach used for this purpose, focusing on quantifying the nitrogen content by converting it into a form that can be measured.
The procedure involves several steps:

• Digestion: The sample is first digested with concentrated sulfuric acid, converting organic nitrogen into ammonium ions ( ext{NH}_4^+).
• Neutralization: The acidic solution is neutralized, typically transforming the ammonium ions into ammonia gas, which is then trapped and measured.
• Titration: The evolved ammonia is usually quantified via titration, often allowing an estimate of the nitrogen content indirectly pointing to protein concentration.

This method is fundamental in fields like agriculture and food science where nitrogen analysis is crucial for determining the nutritional value and quality of substances such as fertilizers and food products.

The Role of Copper Sulfate as a Catalyst in Kjeldahl's Method

In Kjeldahl's method, copper sulfate ( ext{CuSO}_4) serves as an influential catalyst, significantly enhancing the reaction speed during the digestion process. This compound is added as a catalytic agent to boost the breakdown of organic material.
Copper sulfate effectively facilitates the conversion of organic nitrogen into ammonium sulfate by contributing to the oxidative digestion.

Here are some key points regarding ext{CuSO}_4 functioning as a catalyst:

• Enhances the efficiency of sulfuric acid in breaking down proteins into ammonium ions.
• Reduces the time required for complete digestion of samples.
• Improves the accuracy and reproducibility of nitrogen determination in samples.

By using copper sulfate, practitioners attain more consistent results, making ext{CuSO}_4 an essential component in accurately quantifying nitrogen content through Kjeldahl's method.