Problem 26 - A Complete Resource Book in Chemistry for JEE Main

Question

On warming with silver powder, chloroform is converted into (a) hexachloroethane (b) acetylene (c) ethylene (d) carbon

Step-by-Step Solution

Answer

Chloroform is converted into elemental carbon (option d) on warming with silver powder.

Step 1: Understand the Problem

We are given that on warming chloroform with silver powder, a chemical reaction occurs. We need to determine the compound that is formed as a result of this reaction.

Step 2: Reaction of Chloroform with Silver

Chloroform, having the chemical formula \( \text{CHCl}_3 \), reacts with metallic silver. Silver acts as a reducing agent, and this reaction leads to the removal of chlorine atoms from chloroform.

Step 3: Formation of the Compound

As silver reduces chloroform, all three chlorine atoms are removed. This leaves behind carbon, as removing chlorine from \( \text{CHCl}_3 \) (chloroform) eventually leads to the formation of elemental carbon.

Step 4: Identify the Product

Given the options, the formation of elemental carbon aligns with the reaction process where chloroform loses chlorine atoms. Thus, the product formed is carbon (option d).

Key Concepts

Silver as Reducing Agent

Silver serves as a reducing agent in many chemical reactions, but let's make that easy to understand. A reducing agent is a substance that helps another substance gain electrons during a chemical reaction. This means the reducing agent itself loses electrons and is oxidized.
In the context of the reaction between silver and chloroform, silver facilitates the removal of chlorine atoms from chloroform. When silver powder is added to chloroform ( \( \text{CHCl}_3 \)), the silver acts to assist in breaking the bonds between the chlorine atoms and the rest of the molecule. Here, silver's role as a reducing agent is crucial, as it enables the stripping away of all the chlorine atoms, preparing the stage for the formation of elemental carbon. This process happens because silver donates electrons, destabilizing the chlorine from the chloroform.

Chemical Reaction Mechanism

The chemical reaction mechanism describes how a chemical reaction proceeds. It's important to understand this to see how starting materials transform into products. When chloroform ( \( \text{CHCl}_3 \)) reacts with silver, the mechanism involves several steps that result in the breakdown of the original chloroform structure.
Here's a simple breakdown of the steps involved:

• First, the chloroform comes into contact with silver powder.
• The silver acts to destabilize and detach the chlorine atoms from the chloroform molecule.
• As chlorine atoms are removed, they pair up and form chlorine gas, indicated by the release of small gas bubbles if observed during an experimental setup.

The mechanism is efficiently driven by the electrons from the silver, which target the bonds between carbon and chlorine in chloroform, leading to the release of chlorine as a gas and leaving elemental carbon behind. This mechanism showcases the dynamic nature of chemical reactions and how starting compounds undergo transformations to yield new substances.

Elemental Carbon Formation

Elemental carbon refers to carbon in its pure form, and its formation is an intriguing aspect of the reaction involving chloroform and silver. Here's what happens:
As silver reduces chloroform, it removes chlorine atoms from it. What remains after this dechlorination is lone carbon atoms. Initially, these carbon atoms exist in a free state. Due to the nature of carbon, they have strong tendencies to form bonds with each other. This often results in the carbon atoms aggregating to form carbon particles.
Pure carbon can exist in several allotropes, but when formed in such experiments, it typically takes the form of amorphous carbon. This is often a black, powdery substance. This entire process is a great example of how a specific chemical reaction can yield an elemental form of a component, such as carbon, through strategic manipulation with catalysts like silver. Understanding elemental carbon formation provides insight into the fundamental transformations involved in chemical reactions.