Free Experimental Techniques in Chemistry MCQs with Answers

51. In the separating funnel shown, two immiscible layers are formed after shaking. If the solute is more soluble in chloroform, which layer should be collected to obtain the solute?

• A. Upper layer
• B. Lower layer
• C. Both layers
• D. Neither

Explanation: Chloroform (denser) forms the lower layer; solute distributes there due to higher solubility.

52. In the chromatogram shown, two spots (A and B) are observed at different heights from the baseline. Which component exhibits greater solubility in the mobile phase?

• A. A
• B. B
• C. Both
• D. Cannot determine

Explanation: The farther the spot travels, the greater is its solubility in the solvent.

53. What is the theoretical yield (in mL) at STP of hydrogen gas produced when the 0.040 g of Mg reacted completely?

• A. 10 mL
• B. 25 mL
• C. 37 mL
• D. 46 mL
• E. 51 mL

Explanation: The theoretical yield at STP can be found from the chemical equation of the reaction: 0.040 g Mg = x L Mg + 2HCL → MgCl2 + H2 (g) 24.0 g/mol = 22.4 L Solving for x L = 0.037 L or 37 ml

54. What is the pressure of the collected gas once you have also corrected for the vapor pressure of the water?

• A. 730 mm Hg
• B. 727 mm Hg
• C. 30.0 mm Hg
• D. 697 mm Hg
• E. 760 mm Hg

Explanation: Correcting the previous pressure by subtracting the given amount for the vapor pressure of water at 302 K gives you: 727 mm Hg - 30 mm Hg vapor pressure = 697 mm Hg as the final pressure.

55. If the liquid being distilled contains dissolved ammonia gas, where will it be bound after distillation is completed?

• A. Around the thermometer
• B. In the condenser
• C. In the circulating water
• D. In the heated flask
• E. In the distillate

Explanation: Since the dissolved ammonia is volatile below the boiling point of water, it will be found in the distillate. Some will also escape as a gas.

56. Fluted filter paper is used to

• A. FILTER HOT SOLUTION
• B. Avoid premature crystallization
• C. )INCREASE Rate of crystallization
• D. decrease the size

Explanation: The correct option here is (A) FILTER HOT SOLUTIONS.Fluted filter paper is primarily used to filter hot solutions or substances. The fluted design of the filter paper allows for a larger surface area without compromising the filtration speed. This feature is especially useful when dealing with hot solutions that may have impurities or insoluble particles that need to be removed.Let's break down why the other options are incorrect:(b) Avoid premature crystallization: As previously mentioned, fluted filter paper isn't specifically designed to prevent premature crystallization. It's primarily for filtration purposes, providing efficient separation of solids from liquids, especially in hot solutions.(c) INCREASE Rate of crystallization: Fluted filter paper doesn't have any effect on the rate of crystallization. Its purpose is filtration, not altering the kinetics of crystallization processes.

57. Size of filter paper is selected according to the amount of

• A. solution
• B. amount of insoluble solute
• C. amount of soluble solute
• D. Amount of solvents

Explanation: The size of filter paper is generally selected based on the amount of (a) solution being filtered.Here's why the other options are incorrect:(b) The amount of insoluble solute might affect the choice of filtration method but not the size of the filter paper.(c) The amount of soluble solute doesn't necessarily dictate the size of the filter paper; it's more about the total solution volume.(d) The amount of solvent might affect the filtration process but typically doesn't determine the size of the filter paper used

58. Separation of a solid from its hot saturated solution by cooling is called

• A. vapourization
• B. solvent extractio
• C. filtration
• D. crystallization

Explanation: The correct answer is (d) crystallization.Crystallization: This process involves separating a solid from its hot saturated solution by cooling. As the solution cools, the solubility of the dissolved substance decreases, leading to the formation of solid crystals. These crystals can then be separated from the solution.Why the other options are incorrect:(a) Vapourization: Vapourization refers to the phase transition from liquid to gas, which involves the conversion of a substance into its gaseous state, not the separation of a solid from a solution by cooling.(b) Solvent extraction: Solvent extraction is a method used to separate compounds based on their solubility in different solvents. It doesn't involve separating a solid from a solution by cooling; rather, it utilizes the differential solubility of substances in different solvents.(c) Filtration: Filtration is a process used to separate solids from liquids or gases using a filter medium. It doesn't involve the separation of a solid from a solution by cooling; instead, it's a mechanical process to separate solid particles from a liquid or gas by passing it through a filter medium.

59. The use of CaCl2 and PCl5. in the process of crystallization is as a

• A. reducing agent
• B. oxidizing agent
• C. drying agent
• D. coloring agent

Explanation: rying agent in crystallization (option C):CaCl2 and PCl5: These compounds are known for their hygroscopic properties, meaning they have a strong affinity for water. When added to a solution or used in the crystallization process, they act as drying agents by effectively absorbing moisture from the solvent or solution.

60. The solution remaining after the formation of crystals is called

• A. Filtrate, residue
• B. Dilute solution
• C. Residue
• D. both a &b

Explanation: The solution remaining after the formation of crystals is called Mother liquor (Option A):Mother liquor refers to the solution that remains after the crystallization process has occurred and crystals have formed. It contains the excess solute that didn't crystallize out and remains in the liquid phase.Why the other options are incorrect:(c) Residue: Residue typically refers to the solid material left behind after a process. In the context of crystallization, residue might refer to any undissolved impurities or insoluble components that don't form crystals but remain as solid residue.(b) Dilute solution: Dilute solution implies a solution with a relatively low concentration of solute compared to the solvent. The term doesn't specifically refer to the solution remaining after crystallization.(a) Filtrate, residue: The term "filtrate" usually refers to the liquid collected after filtration, containing the dissolved components that pass through the filter paper. It's not the solution remaining after crystallization.