Free Solutions and Colloids MCQs with Answers

81. The arsenius sulphide sol has negative charge the maximum coagulating power for precipitating it is of:

• A. 0.1(N) Zn(NO3)2
• B. 0.1(N) Na3PO4
• C. 0.1(N) ZnSO4
• D. 0.1(N) AlCl3

Explanation: More the valency of cation greater will be its coagulating power as per hardy schulze rule.

82. The coagulation of 100 ml of a colloidal sol of gold is completely prevented by addition of 0.25 g of a substance `X' to it before adding 10 ml of 1% NaCl solution. The gold number of `X' is:

• A. 0.25
• B. 25
• C. 250
• D. 2.5

Explanation: 250 mg of X is present in 100 ml of colloidal sol of gold. By definition, gold no. of X is that amount of it in mg which is present in 10 ml of colloidal gold solution. Hence 19 in 10 ml, the amount of X present is 25 mg which is the gold number of X.

83. The Brownian movement of colloidal particles is because of:

• A. Convection currents in the fluid
• B. Unequal bombardments by the molecules of the dispersion medium on colloidal particles.
• C. Setting of dispersed phase under gravity.
• D. Thermal gradient in the medium.

Explanation: Unequal bombardments of solvent particles on colloidal particles cause zigzag motion.

84. On addition of one ml solution of 10 % NaCl to 10 ml gold sol in the presence of 0.250 g 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: According to the definition of gold number, in this case starch has gold number of 250.

85. For the coagulation of 100 ml of arsenous sulphide sol 4 ml of 1 M NaCl is required. What would be the flocculation value of NaCl?

• A. 40
• B. 20
• C. 60
• D. 80

Explanation: The minimum amount of lyophilic colloid in mg which prevents the coagulation of 10 ml gold sol by 1 ml of 10% NaCl solution. So for 100 ml gold sol by 4 ml of 1 M NaCl solution is 40 ml.

86. Which one of the following statements is incorrect?

• A. A solution freezes at a lower temperature than the pure solvent
• B. A solution boils at a higher temperature than the pure solvent.
• C. 0.1 M NaCl solution and 0.1 m sugar solution have the same boiling point
• D. Osmosis cannot take place without a semi-permeable membrane.

Explanation: Molarity is the moles of solute in 1 litre of solution Molality is the moles of solute per 1 kg of solvent. Therefore, a molal solution is less concentrated than a molar solution because the latter contains less solvent. The answer is C as the elevation of the boiling point depends on the number of particles added to the solution. Since we have NaCl being ionic unlike sugar, NaCl ionizes to give Na ions and Cl ions, doubling the number of particles in the solution, leading to a further elevation in the boiling point.

87. The presence of common ions the solubility of a slightly soluble ionic compound.

• A. decreases
• B. increases
• C. neither decreases nor increases
• D. none

Explanation: The presence of common ions in a solution can affect the solubility of a slightly soluble ionic compound. This phenomenon is described by Le Chatelier's principle.When a common ion is added to a solution containing a slightly soluble salt, the equilibrium shifts toward the side of the reaction that reduces the concentration of that ion. As a result, the solubility of the ionic compound decreases.For example, if you have a solution of a sparingly soluble salt, say AB, and you add a common ion A+ or B− (which comes from another soluble salt), the equilibrium will shift to the left, decreasing the dissociation of AB and reducing its solubility.Therefore, the correct answer is that the presence of common ions decreases the solubility of a slightly soluble ionic compound

88. _ properties depend upon the nature of compound.

• A. Extensive
• B. Intensive
• C. Colligative
• D. Physical

Explanation: The explanation for this question will be added soon.

89. A solution should be:

• A. Homogenous mixture
• B. Colloid
• C. Belong to the same state of matter
• D. All of the above

Explanation: The explanation for this question will be added soon.

90. The energy released when solvent molecules surround the ions in ionic compounds is:

• A. Energy of solution
• B. Enthalpy
• C. Energy of solvation
• D. None of the above

Explanation: The explanation for this question will be added soon.