Free Solutions and Colloids MCQs with Answers

61. The Brownian motion is due to:

• A. Temperature fluctuation within the liquid phase.
• B. Attraction and repulsion between charges on the colloidal particles.
• C. Impact of the molecules of the dispersion medium on the colloidal particles.
• D. Convectional currents.

Explanation: Brownian motion is the random movement of the low weight particles suspended in a fluid.

62. The potential difference between the fixed charged layer and the diffused layer having opposite charge in colloidal solution is called:

• A. electrostatic potential
• B. sedimentation potential
• C. zeta potential
• D. chemical potential

Explanation: The potential differences existing between the surfaces of a solid particle immersed in a conducting liquid (e.g. water) and the bulk of the liquid is called the zeta potential.

63. Gold number is the index for :

• A. the amount of gold present in the colloid.
• B. the amount of gold required to break the colloid.
• C. the amount of gold required to protect the colloid.
• D. none of the above.

Explanation: Gold number is 'least quantity of protective colloid in milligrams, which is just sufficient to prevent the coagulation of 10 ml of standard gold sol (containing 0.0053% gold) by the rapid adidition of 1 ml of 10% NaCl solution. The Coagulation of gold sol is indicated by change in color from red to violet. Thus small the gold number, the greater is protective power of lyophilic colloid.

64. On adding few drops of dil. HCl or FeCl3 to freshly precipitated ferric hydroxide, a red coloured colloidal solution is obtained. This phenomenon is known as:

• A. Peptization
• B. Dialysis
• C. Protection
• D. Dissolution

Explanation: Peptization is the process responsible for the formation of stable dispersion of colloidal particles in dispersion medium.

65. A white precipitate of Sn(OH)4 is peptized with dil. HCl. The sol particle will carry :

• A. Positive charge
• B. Negative charge
• C. Sometimes positive and sometimes negative charge
• D. No charge

Explanation: The sol particle will carry positive charge.

66. The stabilization of the dispersed phase in a lyophobic sol is due to :

• A. The viscosity of the medium
• B. The surface tension of the medium
• C. Both (A) and (B)
• D. The formation of an eletrical layer between the two phases

Explanation: Due to preferential adsorption of similar ions, an electrical double layer formed on the surface of colloidal particles. e.g. arsnius sulphide solution.

67. Gelatin is often used as an ingredient in the manufacture of ice-cream. The reason for this is:

• A. to improve the flavour
• B. to cause the mixture to solidify
• C. to stabilize the colloid and prevent crystal growth
• D. to prevent the formation of a colloid

Explanation: This is due to stabilize the colloid and prevent crystal growth.

68. On adding 1ml solution of 10% NaCl to 10ml gold sol in the presence of 0.25g of starch, the coagulation is just prevented. Starch has the following gold number:

• A. 0.025
• B. 0.25
• C. 2.5
• D. 250

Explanation: Gold number is 'least quantity of protective colloid in milligrams, which is just sufficient to prevent the coagulation of 10 ml of standard gold sol (containing 0.0053% gold) by the rapid adidition of 1 ml of 10% NaCl solution.

69. Choose the correct options regarding a catalyst :

• A. It increases the equilibrium concentration of the products
• B. It is a substance which change the equilibrium constant of the reacting ion.
• C. It shortens the time to reach equilibrium.
• D. It supplies energy to the reaction.

Explanation: A catalyst is substance that increases rate of reaction and it shortens the to reach equilibrium.

70. Purple of Cassius is:

• A. A solution of AgNO3 in HNO3
• B. Colloidal solution of gold
• C. A colloidal solution of platinum
• D. A colloidal solution of palladium

Explanation: Purple of Cassius is colloidal solution of gold. It is formed by the reaction of gold salts with tin(II) chloride.