Question

A bottle of dry ammonia and a bottle of dry hydrogen chloride connected through a long tube are opened simultaneously at both ends, the white ammonium chloride ring first formed will be (a) at the centre of the tube (b) near the hydrogen chloride bottle (c) near the ammonia bottle (d) throughout the length of the tube

Short answer

The ring forms closer to the hydrogen chloride bottle.

Step-by-step solution

Understand the Reaction

When ammonia (NH_3) and hydrogen chloride (HCl) gases diffuse toward each other, they react to form ammonium chloride (NH_4Cl), which appears as a white ring. The equation for the reaction is \( \text{NH}_3 + \text{HCl} \rightarrow \text{NH}_4Cl \).

Key concepts

Ammonia

Ammonia is a colorless gas with a distinct pungent smell. It has the chemical formula \( \text{NH}_3 \). It consists of one nitrogen and three hydrogen atoms, forming a trigonal pyramidal shape. Ammonia is less dense than air, allowing it to rise and spread relatively quickly in a surrounding environment.

In terms of chemical properties, ammonia is a base and can react with acids to form salts. It is highly soluble in water, creating a solution known as ammonium hydroxide. This gas is commonly used in fertilizers, cleaning products, and even for refrigeration purposes.

In the experiment described, ammonia is one of the gases involved in the reaction where it combines with hydrogen chloride to form ammonium chloride. The diffusion of ammonia through the air is crucial to reaching hydrogen chloride so that the reaction can take place.

Hydrogen Chloride

Hydrogen chloride (\(\text{HCl}\)) is a diatomic molecule composed of hydrogen and chlorine atoms. In its gaseous state, it is colorless and has a sharp, irritating odor. Like ammonia, hydrogen chloride is denser than ammonia. However, it is more dense than air. This property affects its diffusion rate in the atmosphere.

Upon dissolution in water, hydrogen chloride forms hydrochloric acid, a strong corrosive acid widely used in industry for refining metals, and for pH balance adjustment in water treatment.

In diffusion studies involving gases like the experiment referenced, hydrogen chloride travels slower through air compared to lighter gases such as ammonia. As hydrogen chloride diffuses through the tube to meet ammonia, a crucial chemical reaction occurs that results in the formation of a visible product.

Ammonium Chloride Reaction

The interaction between ammonia and hydrogen chloride results in the formation of ammonium chloride (\(\text{NH}_4\text{Cl}\)). This is a significant reaction because it showcases the process of gas diffusion leading to a tangible outcome, a visible ring that forms inside the tube. This white ring of ammonium chloride is a solid, and it's often formed earlier at a point closer to the hydrogen chloride source due to its slower diffusion rate compared to ammonia.

The chemical equation representing this reaction is \(\text{NH}_3 + \text{HCl} \rightarrow \text{NH}_4\text{Cl}\). Here, ammonia acts as a base combining with the acidic hydrogen chloride to form the ionic compound ammonium chloride. This compound is widely used in industrial applications such as fertilizers, in medicine as an expectorant, and in the production of dry cells.

The location of the ammonium chloride ring helps visualize the diffusion process, complimenting our understanding of gas diffusion rates where lighter gases move at a faster rate than heavier ones.