Test: Properties of Colloids (Old NCERT) - NEET MCQ

The correct answer is Option B.

It is the migration of electrically charged colloidal particles in one direction under the influence of an electric field. When colloidal particles move towards a positive electrode, they are negatively charged and vice versa. Electrophoresis is used to measure the rate of migration of sol particles

The correct answer is Option C.
The random movement of microscopic particles suspended in a liquid or gas, caused by collisions between these particles and the molecules of the liquid or gas in free space is called Brownian movement.

The correct answer is option C.
1. Minimum quantity of an electrolyte required to cause precipitation of a sol is called its coagulating value.
2. Greater the charge on flocculating ions and smaller is the amount of electrolyte required for precipitation, higher is the coagulating power of coagulating ions (Hardy Schulze Law).
3. Phosphate ion bears −3 charge, sulphate ion bears -2 charge and chloride ion carries only −1 charge and due to high charge the coagulating power of phosphate is higher than chloride.
 

The correct answer is Option D
 When alum is added to raw water it reacts with the bicarbonates alkalinities present in water and forms a gelatinous precipitate.
It neutralizes all the suspended impurities of water resulting in their coagulation.

The Tyndall Effect is the effect of light scattering in colloidal dispersion, while showing no light in a true solution. This effect is used to determine whether a mixture is a true solution or a colloid.

Coagulation is the destabilization of Colloids by neutralizing the electric charge of the dispersed phase particles, which results in aggregation of the colloidal particles.

Lyophilic colloids have a unique property of protecting lyophobic colloids. When a lyophilic sol is added to the lyophobic sol, the lyophilic particles form a layer around lyophobic particles and thus protect the latter from electrolytes. Lyophilic colloids use for this purpose are called protective colloids.

The substance which forms the colloidal solution in water is starch. A colloidal solution is a solution in which the colloid mixes uniformly. All colloids have a Tyndall Effect, which is not exhibited by glucose. Starch is a colloid and thus when mixed with water can form the colloidal solution.

Charge and solvation of the colloidal particles

Lyophilic sols are colloidal solutions in which the dispersed particles have a strong attraction to the solvent. The stability of lyophilic sols is due to the charge and solvation of the colloidal particles. The particles carry a charge and are surrounded by a layer of solvent molecules, known as the solvation layer. This solvation layer acts as a barrier between the particles, preventing them from coming into contact and aggregating. The charge of the particles also helps to repel them and keep them dispersed.

The size of the colloidal particles is not a direct factor in the stability of lyophilic sols. The charge and solvation of the particles are more important in maintaining stability.

Solvation of the colloidal particles is one of the factors that contribute to the stability of lyophilic sols, but not the only one, it should be combined with the charge of the colloidal particles.

The correct answer is Option D.
Electrophoresis movement of colloidal particles towards an electrode, when they are subjected to an electrical field.

The correct answer is option A
In Tyndall effect the colloidally suspended particles trace out the path of the strong beam of light because of scattering of light by the colloidal particles.
 

If FeCl₃ is added to excess of hot water, a positively charged sol of hydrated ferric oxide is formed due to adsorption of Fe³⁺ ions.
Ferric hydroxide is a negative sol,FeCl₃ electrolyte will coagulate the most.

Aggregation of colloidal particles into insoluble precipitate by addition of some suitable electrolyte is called coagulation.

The dispersion of a freshly precipitated material into colloidal solution by the action of an electrolyte in solution is termed peptization. The electrolyte used is called a peptizing agent. For Example, sols obtained by peptization are: Freshly prepared ferric hydroxide on treatment with a small amount of ferric chloride solution at once forms a dark reddish brown solution. Ferric chloride acts as a peptizing agent.

The correct answer is option D
The coagulation of a colloidal solution by an electrolyte does not take place until the added electrolyte has certain minimum concentration in the solution. The minimum concentration of an electrolyte in millimoles per litre required to cause precipitation of a sol in two hours is called coagulating value. The smaller the quantity needed, the higher will be the coagulating power of an ion.

The correct answer is Option D
Fe³⁺
Coagulation power is directly proportional to the magnitude of charge on the ion.
 

Dialysis is a process in which colloid is placed inside a bag made of semi permeable membrane like cellophane or parchment paper which permits ions and not colloids to pass through.

The correct answer is Option A.

AS₂S₃ is an anionic sol (negative sol) hence coagulation will depend on coagulating power of cation , which is directly proportional to the valency of the cation (Hardy-Schulze rule). 
Hence positive ions having maximum amount of charge will have more coagulation thus, Al³⁺ have maximum coagulating power.

The correct answer is Option D
Tyndal effect is scattering of light when a ray of light is passed through a colloidal solution made forming a tyndall cone.