Problem 31 - A Complete Resource Book in Chemistry for JEE Main

Question

Colloidal solution of arsenious sulphide is prepared by (a) hydrolysis (b) double decomposition (c) electrodispersion method (d) peptization

Step-by-Step Solution

Answer

A colloidal solution of arsenious sulphide is prepared by hydrolysis.

Step 1: Understanding the Question

We are asked to identify the method used to prepare a colloidal solution of arsenious sulphide. The options given are different methods of generating colloids.

Step 2: Explanation of Each Method

(a) Hydrolysis involves chemical breakdown by water. (b) Double decomposition occurs when two compounds react to give two new compounds. (c) The electrodispersion method involves breaking down particles through electricity. (d) Peptization is converting precipitate into colloid by shaking with a dispersion medium.

Step 3: Identification of Correct Method

Arsenious sulphide, a sulfide, can be easily prepared as a colloid via the hydrolysis of arsenic compounds in water, forming colloidal particles.

Key Concepts

Arsenious sulphide

Arsenious sulphide, also known as arsenic trisulfide, is a compound composed of arsenic and sulfur. Its chemical formula is As _2 S _3 . This compound is commonly known for its fine yellow powdery appearance. Arsenious sulphide has fascinating properties when it comes to chemistry, especially in the formation of colloidal solutions.
Arsenious sulphide becomes significant when discussing colloidal chemistry because it can form stable colloids. These colloidal solutions have particles dispersed throughout a liquid medium. Preparation via hydrolysis involves treating arsenic compounds with water. This causes the breakdown of the molecular bonds, allowing arsenious sulphide to form as tiny particles. These particles remain dispersed within the solution, creating what we recognize as a colloidal solution of arsenious sulphide.

Hydrolysis

Hydrolysis is a fundamental chemical process involving the reaction of a compound with water. It means 'splitting with water'. During this process, water causes the bonds within a molecule to break down, often transforming the original compound into other products.
There are a few key points about hydrolysis:

• It involves water as a reactant.
• The breaking of chemical bonds is facilitated.
• This process often results in the formation of acids, bases, or other compounds.

Hydrolysis plays a pivotal role in preparing colloids. In the case of arsenious sulphide, arsenic compounds undergo hydrolysis in water, leading to the formation of fine arsenious sulphide particles. These particles are too small to settle or be filtered out easily, thus forming a stable colloidal dispersion.

Colloid chemistry

Colloid chemistry is the study of substances microscopically dispersed throughout another substance. These systems are neither true solutions nor simple suspensions. They exhibit unique properties, such as the Tyndall effect, where light scatters due to the dispersed colloidal particles.
In colloid chemistry:

• Particle sizes range from 1 nm to 1000 nm.
• Colloids can be found in various forms like aerosols, gels, and sols.
• The particles are dispersed and do not settle quickly, maintaining stability.

Colloids are essential in various scientific and industrial applications. Arsenious sulphide in water forms a colloidal system when prepared via hydrolysis. This transformation allows the particles to remain suspended, making the solution stable and unique. Understanding colloid chemistry provides insight into how such dispersed systems behave and are utilized.