Chemistry - Study Mode

[#291] An emulsifier is an agent which
Correct Answer

(A) Stabilises an emulsion

[#292] Muddy water is treated with alum in purification process, it is termed as :
Correct Answer

(D) Coagulation

Explanation

Solution: Natural and wastewater contain small particulates that are suspended in water forming a colloid. These particles carry the same charges, and repulsion prevents them from combining into larger particulates to settle. Historically, dirty water is cleaned by treating with alum, Al 2 (SO 4 ) 3 .12 H 2 O, and lime, Ca(OH) 2 . The phenomenon is known as coagulation.

[#293] Which one of the following is an example of a gel ?
Correct Answer

(C) Face cream

Explanation

Solution: A gel is a solid, jelly-like material that can have properties ranging from soft and weak to hard and tough. Gels consist of a solid three-dimensional network that spans the volume of a liquid medium and ensnares it through surface tension effects. Shaving creams in a can are commonly dispensed as a foam or a gel.

[#294] A substance which readily forms colloidal solution in contact with water is called
Correct Answer

(D) Hydrophilic colloid

Explanation

Solution: A colloidal dispersion in which the dispersed particles are more or less liquid and exert a certain attraction on and absorb a certain quantity of the fluid in which they are suspended is called as hydrophilic colloid. Molecules of a hydrophilic colloid have an affinity for water molecules and when dispersed in water become hydrated. Hydrated colloids swell and increase the viscosity of the system, thereby improving stability by reducing the interaction between particles and their tendency to settle. They may also possess a net surface electrical charge. The charge sign depends on the chemical properties of the colloid and the pH of the system. The presence of a surface charge produces repulsion of the charged particles and thus reduces the likelihood that the particles will adhere to one another and settle. Some examples of hydrophilic colloids used in pharmacy are acacia, methylcellulose, and proteins, such as gelatin and albumin.

[#295] Peptization is a process of
Correct Answer

(D) Dispersing precipitates into colloidal solution

Explanation

Solution: Peptization or Deflocculation is the process responsible for the formation of converting precipitate into colloid by shaking with it an electrolyte. This is particularly important in colloid chemistry or for precipitation reactions in an aqueous solution.