Chromatography & Solvent Extraction — Practice Questions

Free NEET Chemistry multiple-choice questions on Chromatography & Solvent Extraction. Attempt each question and reveal the answer with a full explanation.

In Column Chromatography, the 'stationary phase' is a solid while the 'mobile phase' is a liquid. This mechanism is primarily based on: Adsorption Partition Ion-exchange Size-exclusion Chromatography is classified into different types based on the physical state of the phases and the mechanism of separation. To which category does Paper Chromatography belong? Partition chromatography Adsorption chromatography Ion-exchange chromatography Size-exclusion chromatography In Column Chromatography, the component of the mixture which has the highest adsorption affinity for the stationary phase will: Remain near the top of the column Elute first from the column Move the fastest through the column Dissolve completely in the mobile phase In Thin Layer Chromatography, the mobile phase moves up the stationary phase due to: Capillary action Gravitational force Suction pressure Diffusion Which of the following is commonly used as a stationary phase in Thin Layer Chromatography? Silica gel Water Benzene Alumina powder in water In paper chromatography, the movement of the mobile phase is primarily due to: Capillary action Gravitational force Adsorption Osmotic pressure Which of the following is used as an adsorbent in Column Chromatography? Silica gel Potassium dichromate Sodium chloride Copper sulfate In Thin Layer Chromatography (TLC), the stationary phase is usually a thin layer of adsorbent silica gel supported on: A glass or plastic plate A piece of filter paper A column of alumina A liquid coated on a solid The R f value of a compound in chromatography depends on: Nature of the compound, stationary phase, and mobile phase Only the temperature Only the length of the chromatography paper The amount of compound applied Which gas is used as a carrier in Gas-Liquid Chromatography (GLC)? Helium or Nitrogen Oxygen Carbon dioxide Chlorine The R f value in Thin Layer Chromatography (TLC) is calculated as: Distance moved by the substance from baseline / Distance moved by the solvent front from baseline Distance moved by the solvent front / Distance moved by the substance Total distance of the plate / Distance moved by the substance Distance moved by the substance / Total length of the paper The method used for the separation of a mixture of amino acids where the stationary phase is water held in the pores of cellulose paper is: Partition chromatography Adsorption chromatography Gas chromatography Thin-layer chromatography In adsorption chromatography, the 'eluent' refers to: The solvent or mixture of solvents used to move the compounds The stationary phase used in the column The mixture of compounds to be separated The glass column itself On a Thin Layer Chromatography (TLC) plate, the distance traveled by the solvent front is 12 cm and the distance traveled by compound 'A' is 4.8 cm. The R f value of 'A' is: 0.4 2.5 0.48 0.12 The principle behind differential extraction is the difference in: Solubilities of the compound in different solvents Boiling points of the components Molecular weights of the components Rates of adsorption In paper chromatography, the R f (retardation factor) value is always: Between 0 and 1 . Greater than 1 . Less than 0 . Exactly 1 for all components. The mixture of compounds is separated by a technique where the stationary phase is a solid and the mobile phase is a liquid. This type of chromatography is known as: Adsorption chromatography Partition chromatography Gas-liquid chromatography Thin layer chromatography only Which of the following serves as the 'carrier gas' in Gas Chromatography? Helium Oxygen Carbon dioxide Chlorine Which type of chromatography is Column Chromatography? Adsorption chromatography Partition chromatography Gas-Liquid chromatography Paper chromatography The R f (Retardation factor) value in Thin Layer Chromatography is a characteristic constant for a substance under given conditions. What is the mathematically possible range for R f values? 0 < R f < 1 -1 < R f < 1 Always R f > 1 It can be any positive value Which of the following types of chromatography involves a liquid stationary phase and a gaseous mobile phase? Gas-Liquid Chromatography (GLC) Thin Layer Chromatography (TLC) Paper Chromatography Column Chromatography In the adsorption chromatography technique, the term 'eluent' refers to: The solvent or mixture of solvents used to move the compounds through the column The stationary phase material like alumina or silica gel The process of recovery of components from the adsorbent The mixture of compounds to be separated During the purification of crude sugar, the brown color of the juice is removed by boiling with: Animal charcoal Activated coconut charcoal Fuller's earth Silica gel Which type of chromatography is most suitable for the separation of a mixture of amino acids? Paper chromatography Simple distillation Sublimation Crystallization Which substance is used as a standard for 'retention time' or 'retardation factor' in chromatography to ensure consistency between experiments? A known reference compound (Standard) Distilled water Pure silica gel The solvent front Which property of Alumina ( Al 2O 3 ) makes it a popular stationary phase in Column Chromatography? Its ability to adsorb molecules on its surface via polar interactions. Its low boiling point which prevents sample degradation. Its high solubility in organic solvents like hexane. Its ability to react chemically with the solutes. Which of the following describes the principle of 'Differential Extraction'? An organic compound is more soluble in an organic solvent than in water. An organic compound has the same solubility in all solvents. Organic compounds are always more soluble in water than in ether. Solubility is independent of the temperature of the solvent. If the R f value of a component in a TLC experiment is 0 , it means: The component has not moved from the baseline. The component moved as fast as the solvent front. The component is highly soluble in the mobile phase. The experiment was a failure. In the context of chromatography, what is 'elution'? The process of washing out adsorbed components from the stationary phase using a solvent. The process of applying the sample onto the stationary phase. The visible color change observed on a TLC plate. The evaporation of the mobile phase at the end of the experiment. Thin Layer Chromatography (TLC) plates are sometimes visualized by placing them in a closed jar containing iodine crystals. This works because: Organic compounds adsorb iodine to form brown spots Iodine reacts chemically to form colored salts Iodine acts as a mobile phase Iodine causes the spots to fluoresce In chromatography, the 'mobile phase' is defined as: The phase that moves through the stationary phase carrying the components The phase that remains fixed on the support The solvent that is used to wash the adsorbent initially The liquid trapped inside the pores of the paper In chromatography, the retardation factor ( R f ) is always less than or equal to 1 because: The solute cannot travel faster than the solvent front The solvent travels faster than the stationary phase The R f value is a ratio of time, not distance Adsorption is always stronger than elution In paper chromatography, the stationary phase used is usually: Water molecules trapped in the cellulose of paper Silica gel Alumina The organic solvent In paper chromatography, why must the spot of the mixture be placed above the level of the solvent in the jar? To prevent the components from dissolving directly into the bulk solvent To allow the solvent to evaporate more quickly To ensure the R f value is greater than 1 To keep the stationary phase dry For a given volume of solvent, the efficiency of differential extraction is higher when: The solvent is used in multiple small installments The entire volume of solvent is used in a single extraction The temperature of the extraction is kept very low The density of the solvent is equal to the aqueous layer The principle of 'differential extraction' is based on the distribution of a solute between two immiscible solvents. Which law governs this process? Nernst Distribution Law Henry's Law Raoult's Law Dalton's Law Partition chromatography is based on the continuous differential distribution of components of a mixture between: Stationary and mobile liquid phases Solid stationary and liquid mobile phases Solid stationary and gaseous mobile phases Liquid stationary and liquid mobile phases only The stationary phase in paper chromatography is accurately described as: Water molecules trapped in the cellulose network of the paper The cellulose fibers of the paper itself The organic solvent moving up the paper The silica gel coating on the paper The correct order of elution of four compounds A, B, C, and D from a silica gel column, if their adsorption affinity is A > C > B > D , is: D, B, C, A A, C, B, D D, C, B, A A, B, C, D In the process of differential extraction, which of the following practices increases the efficiency of extracting a solute from an aqueous layer into an organic solvent? Extracting multiple times with small volumes of organic solvent Extracting once with a very large volume of organic solvent Increasing the temperature of the aqueous layer Adding more water to the separating funnel In Thin Layer Chromatography (TLC), what determines the speed at which a component moves up the plate? The balance between its affinity for the stationary phase and its solubility in the mobile phase. Only the molecular weight of the component. The boiling point of the solvent used as the mobile phase. The thickness of the glass plate. Which of the following statements about the 'retention time' in chromatography is correct? It is the time taken by a component to travel from the injection point to the detector. It is independent of the flow rate of the mobile phase. It is the same for all components in a mixture. It is measured only in paper chromatography. Which of the following statements is TRUE regarding the 'solvent extraction' or 'differential extraction' technique? Extraction is more efficient when the solvent is used in multiple small installments rather than one large volume The solute must be less soluble in the organic solvent than in water The two solvents used must be completely miscible with each other It is used to separate two solids with different melting points In Paper Chromatography, the stationary phase is considered to be: Water molecules trapped in the cellulose fibers of the paper The cellulose of the paper itself The organic solvent used as the mobile phase The silica gel coated on the paper Chromatography is used for the separation of: Small amounts of mixtures Only gases Only colored compounds Binary mixtures only Which of the following factors does NOT affect the R f value of a compound in Thin Layer Chromatography? The size of the chromatography plate The nature of the stationary phase The nature of the mobile phase The temperature Which of the following is most likely to be the stationary phase in Gas-Liquid Chromatography (GLC)? A high boiling point liquid coated on a solid support. An inert gas like Helium. A fine powder of Silica gel. A strip of cellulose paper. In Gas Chromatography, the stationary phase is most likely to be: A high boiling point liquid supported on a solid A porous solid like Alumina An inert gas like Helium Water held in cellulose fibers In chromatography, 'Reversed-Phase Chromatography' refers to a system where: The stationary phase is non-polar and the mobile phase is polar The stationary phase is polar and the mobile phase is non-polar The mobile phase moves from top to bottom The R f values are calculated in reverse order The efficiency of differential extraction increases when the extraction is carried out: Multiple times with small volumes of solvent Once with a large volume of solvent At a very high temperature Using a solvent with a lower distribution coefficient In thin-layer chromatography, if the solvent front reaches the top of the plate ( 10 cm) and a spot moves 6 cm, and the polarity of the solvent is increased, what usually happens to the R f value? It increases It decreases It remains unchanged It becomes zero Which reagent is used as a 'developer' or 'visualizing agent' specifically for the detection of amino acids on a paper chromatogram? Ninhydrin solution Iodine crystals Bromine water Potassium permanganate The efficiency of 'differential extraction' using a separating funnel increases when: A given volume of solvent is used in multiple smaller portions A given volume of solvent is used in one single portion The temperature of the solvent is increased significantly The volume of the aqueous layer is increased Which type of chromatography is most effective for separating a mixture of non-volatile organic compounds that have very similar R f values but different polarities? High-Performance Liquid Chromatography (HPLC) Simple Paper Chromatography Steam Distillation Thin Layer Chromatography (TLC) In Thin Layer Chromatography (TLC), if the stationary phase is silica gel (polar) and the mobile phase is hexane (non-polar), which of the following compounds will move the slowest? Carboxylic acids Alkanes Alkenes Aldehydes The separation of a mixture by Column Chromatography depends on the relative rates at which the components of the mixture are: Adsorbed on the stationary phase Dissolved in the stationary phase Evaporated into the gas phase Precipitated by the eluent In the Kjeldahl's method for estimation of nitrogen present in a soil sample, ammonia evolved from 0.75 g of sample neutralized 10 mL of 1 M H2SO4 . The percentage of nitrogen in the soil is : 37.33 45.33 35.33 43.33 The correct order of increasing adsorption of the following groups on a stationary phase (silica gel) in column chromatography is: -CH 3 < -OCH 3 < -COOR < -OH -OH < -COOR < -OCH 3 < -CH 3 -COOR < -OH < -CH 3 < -OCH 3 -OCH 3 < -CH 3 < -OH < -COOR In differential extraction, the efficiency of extracting a solute from an aqueous phase into an organic phase is governed by the Nernst Distribution Law. Which condition makes the extraction more efficient? Using the organic solvent in multiple small portions Using the organic solvent in one large portion Decreasing the volume of the organic solvent Increasing the temperature of the aqueous phase Which of the following is an example of 'Partition Chromatography'? Paper chromatography Column chromatography Thin layer chromatography Gas-solid chromatography Which gas is commonly used as a carrier gas in Gas-Liquid Chromatography (GLC)? Helium Oxygen Carbon dioxide Ammonia If the components of a mixture are visible as colored spots on a Thin Layer Chromatography (TLC) plate, they are identified directly. However, for colorless compounds, which of the following is commonly used for visualization? Iodine crystals in a closed jar Concentrated sulfuric acid spray Distilled water mist Dilute sodium hydroxide solution