Free Solutions and Colloids MCQs with Answers

91. Which term describes a solution in which dissolved solute is in equilibrium with undissolved solute?

• A. Dilute
• B. Saturated
• C. Unsaturated
• D. Supersaturated

Explanation: A solution in which the maximum amount of solvent has been dissolved. Any more solute added will sit as crystals on the bottom of the container.

92. The essential property of a fertilizer is that is should be:

• A. Immiscible
• B. Highly soluble
• C. Insoluble
• D. Partially soluble

Explanation: There are three essential plant nutrients for healthy growth: nitrogen (N), phosphorous (P), potassium (K). Fertilisers contain one or more of these nutrients and different crops require different proportions of each of the three. For the fertiliser to be effective, it must be soluble so that it can reach the plant's roots.

93. Osmotic pressure of a solution is _ property.

• A. Obligative.
• B. Fractional.
• C. Colligative
• D. Automated.

Explanation: Osmotic pressure is a 'colligative' property, like freezing point depression, which means that it depends on the number of particles in solution but not on their chemical identity

94. The vapor pressure lines for pure as well as solutionsof different concentrations are shown. Which line represents pure water?

• A. 1
• B. 2
• C. 3
• D. 4

Explanation: Pure water (with the highest vapor pressure) will boil at the lowest temperature.Boiling occurs when vapor pressure = external pressure.Since pure water already has a higher vapor pressure, it reaches that point sooner - i.e., at a lower temperature

95. 36 g of HCl dissolves in 100 g of solution. The density of HCl is 1.19 gcm-3. The molar mass of the HCl solution will be:

• A. 36.5 g/mol
• B. 38.0 g/mol
• C. 100 g/mol
• D. 11.73 g/mol

Explanation: Explanation:Ar of H is 1 and Ar of Cl is 35.5. Mr = 35.5 + 1 = 36.5 g/mol

96. Seawater has 5.65 x 10^-3 g of dissolved oxygen in one kilogram of water. Concentration of O2 in parts per million is

• A. 5.65
• B. 7.69
• C. 5.20
• D. 4.11

Explanation: A is correct since the solution is given asGiven: Water = 103 g(1 kg), Oxygen = 5.65 x 10-3 gRequired : Oxygen in ppm = ?Formula : Ppm = value in gram / amount of water ( solvent ) x 106Ppm = 5.65 x 10-3 / 103 x 106 = 5.65ppmB, C and D are incorrect because these are not correct values in ppm

97. Lowering in vapour pressure is the highest for:

• A. 0.2 M urea
• B. 0.1 M Glucose
• C. 0.1 M MgSO4
• D. 0.1 M BaCl2

Explanation: The higher the vanthoff factor, the greater the lowering of vapor pressure. The highest van der hoff factor is for BaCl2On dissociation, it gives 3 moles of ions (2 chloride and one barium). So the highest lowering of vapor pressure will be for BaCl2.

98. Water has a vapor pressure of 23.75 at 250c what is the vapor pressure of a solution sucrose if its mole fraction is 0.25?

• A. 15.2 torr
• B. 17.8 torr
• C. 23.8 torr
• D. 29.7 torr

Explanation: Mole fraction of the solute = xs = 0.25Pressure of the solvent = PH2O = 23.76 torrFirst, we solve for the mole fraction of the solvent.x(H2O) = 1 - 0.25 = 0.75Now, we can solve for the pressure of the solution:P(sol) = (xH2O)(PH2O)= (0.75) (23.76 torr)P(sol) = 17.82 torrTherefore, the vapor pressure of the solution is 17.82 torr.

99. Pure water freezes at 0 oC and boils at 100 oC at standard conditions. Calcium chloride was added to pure water. What do you expect about its freezing point and boiling point?

• A. No change in its freezing point and boiling point
• B. Freezing point increases and boiling point decreases.
• C. Freezing point increases and boiling point increases
• D. Freezing point decreases and boiling point increases

Explanation: The presence of impurities in a substance lowers the melting point but increases the boiling point of the substance.

100. The osmotic pressure of dilute solution is given by the formula:

• A. π = nRT/V
• B. π = PRT
• C. π = CRT
• D. π = PV=nRT

Explanation: The correct formula for the osmotic pressure of a dilute solution is π = CRT, where:C is the molar concentration of the solute.R is the universal gas constant.T is the absolute temperature.Option A presents the ideal gas law, which is not applicable to osmotic pressure. Option B lacks the concentration term necessary for calculating osmotic pressure. Option D is another form of the ideal gas law, irrelevant to the context of osmotic pressure.