Free Solutions and Colloids MCQs with Answers

51. When the particle size of dispersed phase in colloidal solution increases :

• A. the Brownian motion become fast
• B. the Brownian motion becomes slow
• C. Brownian motion remains same
• D. none of these

Explanation: Brownian movement is due to the unequal bombardments of the moving molecules of dispersion medium on colloidal particles. Bigger size of particle reduces the momentum.

52. Find the incorrect statement:

• A. As2S3 , Au in their colloidal sols are negatively charged
• B. Fe(OH)3 , Al(OH)3 are positively charged in their colloidal sols.
• C. Ag & Pt are positively charged in their colloidal sols.
• D. smoke is dispersion of positively charged colloidal particles of carbon in air

Explanation: Ag & Pt are negatively charged. They move towards anode in electrophoresis.

53. The presence of soluble soap as a emulsifying agent generally forms the formation of emulsion of :

• A. oil in water
• B. water in oil
• C. both type
• D. none

Explanation: Emulsification takes place by reduction of interfacial tension between two phases. The presence of soluble soaps as the emulsifying agent generally favours the formation of emulsion of oil-in-water type, whereas the presence of insolube soaps (containing non-alkali metal atoms) favour the formation of emulsions of water-in-oil type

54. For the coagulation of 100 mL of As2S3 sol, 5 mL of 1 M NaCl is required. The flocculation value of NaCl is:

• A. 50
• B. 5
• C. 47.6
• D. None of these

Explanation: Millimoles of NaCl added = 5 Volume of the sol containing NaCl solution = 100 mL. Floccul ation value is the amount of electrolyte (in millimoles) that must be added to 1L of the colloidal solution so as to bring about complete coagulation.

55. A substance which completely destroys or reduces the activity of the catalyst is called :

• A. Catalyst
• B. Inhibitor
• C. Promotor
• D. Poison

Explanation: Poison, which come from the reacting substances or products of the reaction itself, accumulate on the surface of solid catalysts and cause their effectiveness to decrease.

56. Adsorption isostere is :

• A. The curve showing the effect of temperature on the extent of adsorption at a given pressure
• B. The curve showing the variation of pressure with temperature, for a given amount of adsorption.
• C. The curve showing the variation of adsorption with pressure at a constant temperature.
• D. A line parallel to x-axis.

Explanation: The adsorption isostere is relation of the equilibrium pressure to the temperature at a constant value of the amount, or excess amount, of substance adsorbed by a given amount of solid.

57. The migration of positively-charged colloidal particles under an electrical field, towards the cathode is called :

• A. Cataphoresis
• B. Electrosmosis
• C. Sedimentation
• D. Electrodialysis

Explanation: If the experiment is set such that only the colloidal particles are allowed to move and not the dispersion media particles it is known as cataphoresis or electrophoresis.

58. After increasing temperature, the rate of physiosorption :

• A. Will Decrease
• B. will Increase
• C. Remain same
• D. cannot say

Explanation: Physisorption is exothermic in nature. Therefore, After increasing temperature, the rate of physiosorption will derease.

59. Which reaction gives colloidal solution :

• A. Option A
• B. Option B
• C. Option C
• D. Option D

Explanation: Colloidal solution of Sulpher is formed.

60. If all the electrolytes are removed from the colloid by persistent dialysis then:

• A. Colloid becomes extremely stable
• B. Colloids get coagulated
• C. No effect is observed
• D. Colloids convert into true solution

Explanation: If all ions are removed the colloidal particles get neutrelized and associate with each other forming suspensions.