Chemistry · Science General

Separation Techniques

842 Questions

Separation techniques involve physical methods to isolate mixtures, including distillation, filtration, and crystallization. Competitive exams frequently test these foundational concepts. Review the exact processes to enhance problem solving speed.

Distillation and evaporationCrystallization processFiltration methodsSeparating dissolved solidsChromatography and mass techniques

Separation Techniques Questions

Multiple choice

Which of the following techniques of chromatography is performed on a sheet of glass, plastic, or aluminum foil?

  1. Column chromatography

  2. Planar chromatography

  3. Paper chromatography

  4. Thin layer chromatography
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Thin layer chromatography (TLC) is a chromatography technique used to separate mixtures. Thin layer chromatography is performed on a sheet of glass, plastic, or aluminum foil, which is coated with a thin layer of adsorbent material, usually silica gel, aluminium oxide, or cellulose (blotter paper).

Multiple choice

Chromatography may be preparative or analytical. In which of the following chromatographic techniques, both the stationary and mobile phases are liquids?

  1. Reversed-phase chromatography

  2. Pyrolysis gas chromatography

  3. Fast protein liquid chromatography

  4. Countercurrent chromatography
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Countercurrent chromatography (CCC) is a type of liquid-liquid chromatography, where both the stationary and mobile phases are liquids. The operating principle of CCC equipment requires a column consisting of an open tube coiled around a bobbin.

Multiple choice

The chromatography technique used for the separation of stereoisomers is

  1. ion exchange chromatography

  2. size-exclusion chromatography

  3. reversed-phase chromatography

  4. chiral chromatography
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Chiral chromatography involves the separation of stereoisomers.To enable chiral separation to take place, either the mobile phase or the stationary phase must be made chiral, giving differing affinities between the analytes.

Multiple choice

The aim of chromatography is to separate the components of a mixture. Which of the following chromatography processes is always carried out in a column?

  1. Gas chromatography

  2. Liquid chromatography

  3. Affinity chromatography

  4. Supercritical fluid chromatography
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Gas chromatography (GC), also known as Gas-Liquid chromatography, (GLC), is a separation technique in which the mobile phase is a gas. Gas chromatography is always carried out in a column which is typically packed or capillary.

Multiple choice

Which of the following statements is/are true? A. In column chromatography, the more highly absorbed component is eluted with less polar solvents. B. Benzoic acid can be extracted from water using ethanol. C. Number of replaceable hydroxyl ions present in one molecule of a base is called its acidity.

  1. Only A

  2. Only B

  3. Only C

  4. A and B

  5. B and C
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

This option is correct because number of replaceable hydroxyl ions present in one molecule of a base is called its acidity is true statement.

Multiple choice

The highest probability of obtaining a pure culture lies in

  1. pour plate method

  2. spread plate method

  3. streak plate method

  4. inoculating a slant
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

The most probable method of obtaining a pure culture is by streak plate method. Individual colonies can be obtained in the fourth quadrant.

Multiple choice

Directions: The first and the last sentences of the passage are numbered 1 and 6, respectively. The rest of the passage is split into four parts named A, B, C and D. These four parts are not given in their proper order. Read the sentences and find out which of the following combinations is correct.

  1. Chromatography is used to separate mixtures of substances into their components. A. Different components travel at different rates. B. The mobile phase flows through the stationary phase and carries the components of the mixture with it. C. They all have a stationary phase (a solid or a liquid supported on a solid) and a mobile phase (a liquid or a gas). D. All forms of chromatography work on the same principle.
  2. In paper chromatography, the stationary phase is a very uniform absorbent paper, while the mobile phase is a suitable liquid solvent or mixture of solvents.

  1. CADB

  2. DCBA

  3. DBCA

  4. ADBC

  5. CDBA
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

“They all have” in C refers to “the same principle” in D, so C follows D. B provides an explanation of the components mentioned in C (general to specific), so B follows C. Hence, the answer is DCBA.

Multiple choice

Ethyl alcohol is mixed completely with water. How ethyl alcohol is separated from the mixture?

  1. By separation flannel

  2. By evaporation

  3. Partial distillation

  4. Evaporation of water
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Fractional distillation (partial distillation) separates miscible liquids with different boiling points. Ethanol boils at 78°C while water boils at 100°C, so repeated vaporization-condensation cycles can enrich the ethanol content. Simple evaporation wouldn't work as both components would evaporate, and 'separation flannel' is not a standard separation technique.

Multiple choice

A mixture of salt and sand can be separated by

  1. sublimation

  2. dissolving water

  3. gravity separation

  4. dry distillation
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Salt (NaCl) is water-soluble while sand (SiO2) is not. Adding water dissolves the salt, leaving sand as insoluble residue. The salt can then be recovered by evaporating the water. The option wording 'dissolving water' is awkward but the intended meaning is correct.

Multiple choice

A mixture of water and alcohol can be separated by ____.

  1. Filtration

  2. Evaporation

  3. Distillation

  4. Decantation
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

A mixture of water and alcohol can be separated by distillation (option C). Distillation works because water and alcohol have different boiling points (100°C for water, 78°C for ethanol), allowing the alcohol to vaporize first. Filtration separates solids from liquids, evaporation leaves solids behind, and decantation separates immiscible liquids of different densities.

Multiple choice

A mixture of iron filings and sand can be separated by ______.

  1. Heating

  2. Sublimation

  3. Hand picking

  4. Magnetic separation
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Iron filings are magnetic and can be attracted by a magnet while sand is non-magnetic. This property difference allows magnetic separation to effectively isolate the iron from the sand mixture.

Multiple choice

Name the process which is used to separate various constituents of petroleum.

  1. Oil refinery

  2. Distillation

  3. Petroleum refinery

  4. Refining
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Oil refinery and petroleum refinery are the places where petroleum is separated into its constituents. Distillation is the process of separating a mixture of two miscible liquids having a boiling point difference more than 25 k. Crude oil is a mixture of many products having a difference of less than 25 k in the boiling points. Refining is the process by which petroleum is separated into its various constituents by fractional distillation.

Multiple choice

A mixture of water and alcohol can be separated by

  1. filtration

  2. distillation

  3. evaporation

  4. decantation

Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Water and alcohol form a homogeneous mixture that cannot be separated by filtration, decantation, or simple evaporation. Distillation works because water (boiling point 100°C) and ethanol (78°C) have different boiling points, allowing them to be separated through controlled heating and condensation.