Free Experimental Techniques in Chemistry MCQs with Answers

1. Which of the following techniques is used for the separation of insoluble Particlesfrom liquids?

• A. Filtration
• B. Crystallization
• C. solvent extraction
• D. Chromatography

Explanation: Filtration involves passing a mixture through a filter that allows the liquid to pass through while trapping the insoluble particles. This method is effective when dealing with a mixture where one component is insoluble and needs to be separated from the liquid phase.

2. Which of the following ways is used for classification of chromatography?

• A. Shape
• B. Phase
• C. Solvent extraction
• D. all

Explanation: Chromatography can be classified based on different mechanisms used for the separation of components in a mixture. These mechanisms include various types such as:Adsorption Chromatography: Separation based on the adsorption of compounds onto a stationary phase.Partition Chromatography: Separation based on differences in partitioning behavior between a mobile and a stationary phase.Ion-exchange Chromatography: Separation based on ionic interactions between charged compounds and a stationary phase carrying opposite charges.Size-exclusion Chromatography: Separation based on differences in molecular size and shape, allowing smaller molecules to enter pores of the stationary phase while larger molecules pass through faster.Why other options are incoorect:(a) Shape: Chromatography isn't primarily classified based on shape. While the shape of molecules might influence their behavior in certain chromatographic techniques, it's not a primary classification method for chromatography.(b) Phase: Refers to the different phases used in chromatography (stationary and mobile), which are integral to the process but don't constitute a classification method for chromatography itself.(d) All: While chromatography encompasses various aspects such as the shape of molecules and phases used, the primary classification is based on the mechanism by which separation occurs, making (c) mechanism the most fitting choice for the classification of chromatography.

3. substance having very high vapour pressure at its melting point, on heatingwill show

• A. Melting
• B. Sublimation
• C. Decomposition
• D. Condensation

Explanation: High vapor pressure at the melting point indicates that the substance readily transitions from its solid phase to its vapor phase without passing through the liquid phase. This process is known as sublimation. When the substance is heated, it will directly convert from a solid to a vapor without melting into a liquid.Let's discuss why the other options might not apply:(a) Melting: If a substance has a very high vapor pressure at its melting point, it implies that the pressure of its vapor is quite significant even at that temperature. This would suggest that the substance tends to skip the liquid phase and directly transition from solid to vapor, rather than melting.(c) Decomposition: High vapor pressure at the melting point doesn't necessarily imply decomposition. While some substances might decompose at high temperatures, the focus here is on the behavior of the substance at its melting point.(d) Condensation: This process involves the transition from a vapor to a liquid upon cooling. However, in the scenario described (a substance with high vapor pressure at its melting point), the substance would likely bypass the liquid phase and undergo sublimation instead of condensation.

4. Branch of chemistry that deals with e complete qualitative and quantitaive analysis of a substance

• A. Stoichio chemistry
• B. Analytical chemistry
• C. Physical chemistry
• D. quantum chemistrY

Explanation: The correct option is:(c) Analytical chemistry.Explanation:Analytical chemistry focuses on the qualitative and quantitative analysis of substances. It involves methods and techniques to identify the components present in a sample (qualitative analysis) and determine their concentrations or amounts (quantitative analysis). This field employs various tools and methodologies like spectroscopy, chromatography, titration, and other analytical techniques to assess and quantify substances accurately.Now, let's explore why the other options are incorrect:(a) Stoichiometry:

5. Rate of filtration can be increased by applying gentle suction

• A. Gooch crucible
• B. Filter paper
• C. Sintered crucible
• D. All of the abovE

Explanation: The correct option, "All of the above," is accurate because applying gentle suction can enhance the filtration rate across various mediums used in laboratory filtration processes:Gooch crucible: Applying gentle suction helps draw the liquid through the porous material (such as the porous bottom of the Gooch crucible), expediting the filtration process by increasing the flow rate.Sintered crucible: Sintered crucibles have a porous structure that allows for filtration without needing additional filter paper. Applying gentle suction aids in pulling the liquid through these porous structures, facilitating faster filtration.Filter paper: When using filter paper in a funnel, applying gentle suction via a vacuum flask or a pump accelerates the passage of liquid through the paper due to the pressure difference created, hence boosting the filtration rate.

6. Which of the following technique is simple and efficient to purify a substance

• A. Filtration
• B. Sublimation
• C. (c) Crystallization
• D. Solvent extraction

Explanation: Among the options provided, (c) Crystallization is often considered a simple and efficient technique for purifying a substance.Explanation:Crystallization: This process involves dissolving a substance in a suitable solvent at an elevated temperature and then allowing the solution to cool. As it cools, the solute precipitates out in the form of crystals, separating from impurities in the solution. Crystallization is efficient because it relies on the differences in solubility between the desired compound and impurities, allowing for purification.While the other techniques mentioned can also purify substances to some extent:Filtration: Useful for separating solids from liquids or gases but might not be as effective for purification unless the impurities are significantly larger than the desired substance.Sublimation: Involves the direct transition of a substance from a solid to a gas state and back to a solid. While effective for certain compounds that undergo sublimation, it's limited to substances that exhibit this behavior.Solvent extraction: Useful for separating compounds based on their solubility in different solvents but might require multiple steps for purification and might not always lead to high purity.

7. Direct conversion of solids into vapors is called

• A. sublimation
• B. Solvent extraction
• C. vaporization
• D. crystallization

Explanation: Sublimation (Option B):Sublimation is a phase transition process where a substance transitions directly from its solid state to its gaseous state without passing through the liquid phase.Under specific temperature and pressure conditions, certain solids possess a vapor pressure that exceeds atmospheric pressure, allowing them to sublime. During sublimation, the solid substance bypasses the liquid phase and transforms into a vapor.Why the other options are incorrect:(a) Solvent extraction: Solvent extraction refers to a method of separating compounds based on their solubility in different solvents. It does not involve the direct conversion of solids into vapors.(d) Vaporization: Vaporization is a general term encompassing both evaporation (conversion of liquids to vapors) and sublimation (conversion of solids to vapors). However, vaporization specifically refers to the phase transition of liquids to vapors and doesn't specifically denote the direct conversion of solids into vapors.(c) Crystallization: Crystallization is a process where dissolved solutes in a solvent form crystals as the solvent evaporates or cools, but it does not involve the direct conversion of solids into vapors

8. Repeated extraction using small portions of solvents is more

• A. Reliable
• B. Efficient
• C. Rapid
• D. slow

Explanation: Repeated extraction using small portions of solvents being more Efficient (Option B):

9. Which is not related pair of term used in analytical techniques

• A. Filtrate, residue
• B. ) Sublimate, sublimation
• C. Drying, desiccator
• D. Separating funnel, mother liquor

Explanation: Not a related pair of terms used in analytical techniques (Option B - Sublimate, sublimation):Sublimate refers to the material that undergoes sublimation, i.e., transforms from a solid to a vapor without going through a liquid phase.Sublimation is the phase transition of a substance directly from a solid to a gas without passing through the liquid phase.These terms are directly related to each other, describing the process and the material undergoing sublimation.Why the other options are incorrect:(a) Filtrate, residue: Filtrate refers to the liquid that passes through the filter paper during filtration, while residue refers to the solid material left behind on the filter paper. These terms are related to each other in the process of filtration.(c) Drying, desiccator: Drying refers to the removal of moisture or liquid from a substance, while a desiccator is a container used to maintain a low-humidity environment. These terms are related as they both involve the control of moisture content, often in analytical techniques.(d) Separating funnel, mother liquor: A separating funnel is used for liquid-liquid extractions, while mother liquor refers to the solution remaining after crystallization. Although they represent different processes, they are related in the context of separating components in analytical techniques.

10. While calculating vapor pressure of a liquid in manometer, the column of mercury facing the vapors of a liquid is _ due to pressure on surface of liquid in flask.

• A. Compressed
• B. Depressed
• C. Rises
• D. Lowers

Explanation: This question, like many of the 2021 PMC practice tests, is a direct line from the Punjab textbook. Please refer to section 4.2.2: Measurement of Vapour Pressure in the grade 11 chemistry book.