Chromatography UPDATED ACTUAL
Exam Questions and CORRECT Answers
Use of chromatography and different types - CORRECT ANSWER - - Chromatography is
useful because it enables the separation, isolation, purification, and identification of components
of extremely complex mixtures
- There are different chromatography techniques:
- Paper chromatography
- Column chromatography
- Thin layer chromatography
- The results of chromatographic analysis are called chromatograms
- The number of spots or peaks correspond to the number of components in the sample
- If only one spot appears, then the substance being tested is pure
- Identification can be carried out in planar chromatography by matching colour or distance of an
unknown sample with reference compounds
Paper chromatography - CORRECT ANSWER - - If a mixture is dropped onto a piece of
blotting paper, the components spread out
- The degree of spreading depends on how well the components stick to the solvent molecules
present in the piece of paper
- Th components which have the least solubility in the solvent are those which tend to stick to the
paper and so do not spread out as much as those which are. more soluble in the solvent (so they
tend not to stick and therefore spread further up the paper)
Adsorption chromatography - CORRECT ANSWER - - Adsorption chromatography
involves the use of a stationary phase and a mobile phase to separate the components of a
mixture
- Adsorption is the attachment of molecules to the surface of a solid, and it occurs when
secondary bonds form between molecules and atoms at the surface of the solid
- The compound most like the mobile phase in polarity will move the furthest along the
stationary phase
, Stationary phase - CORRECT ANSWER - - The material onto which the components of
the mixture adsorb
- Usually a silicate and can be either non-polar, polar, or even ionic
Mobile phase - CORRECT ANSWER - - The liquid (or gas) that moves across the
stationary phase, carrying the mixture to be separated
- It is the solvent and is either a gas, a liquid, or a gel
Rate of movement - CORRECT ANSWER - - The rate of movement of each component is
dependent on the amount of secondary bonding between the components and the stationary or
mobile phase
- The compound most like the mobile phase in polarity will move the furthest and/or the fastest
along the stationary phase
Examples of chromatography
(4) - CORRECT ANSWER - 1. Thin layer chromatography (TLC)
- Involves the stationary phase (usually silicates, or sometimes aluminates) attached to an
aluminium plate
2. Flash/Column chromatography
- A glass tube is filled with the stationary phase (silicates and/or aluminates)
3. High pressure liquid chromatography (HPLC)
- A metal tube filled with the stationary phase and the mobile phase pumped through at high
pressure
4. Gas chromatography
- Similar stationary phase column, but the mobile phase is a gas
- These examples are widely used techniques for separating and identifying the components of
mixtures
Exam Questions and CORRECT Answers
Use of chromatography and different types - CORRECT ANSWER - - Chromatography is
useful because it enables the separation, isolation, purification, and identification of components
of extremely complex mixtures
- There are different chromatography techniques:
- Paper chromatography
- Column chromatography
- Thin layer chromatography
- The results of chromatographic analysis are called chromatograms
- The number of spots or peaks correspond to the number of components in the sample
- If only one spot appears, then the substance being tested is pure
- Identification can be carried out in planar chromatography by matching colour or distance of an
unknown sample with reference compounds
Paper chromatography - CORRECT ANSWER - - If a mixture is dropped onto a piece of
blotting paper, the components spread out
- The degree of spreading depends on how well the components stick to the solvent molecules
present in the piece of paper
- Th components which have the least solubility in the solvent are those which tend to stick to the
paper and so do not spread out as much as those which are. more soluble in the solvent (so they
tend not to stick and therefore spread further up the paper)
Adsorption chromatography - CORRECT ANSWER - - Adsorption chromatography
involves the use of a stationary phase and a mobile phase to separate the components of a
mixture
- Adsorption is the attachment of molecules to the surface of a solid, and it occurs when
secondary bonds form between molecules and atoms at the surface of the solid
- The compound most like the mobile phase in polarity will move the furthest along the
stationary phase
, Stationary phase - CORRECT ANSWER - - The material onto which the components of
the mixture adsorb
- Usually a silicate and can be either non-polar, polar, or even ionic
Mobile phase - CORRECT ANSWER - - The liquid (or gas) that moves across the
stationary phase, carrying the mixture to be separated
- It is the solvent and is either a gas, a liquid, or a gel
Rate of movement - CORRECT ANSWER - - The rate of movement of each component is
dependent on the amount of secondary bonding between the components and the stationary or
mobile phase
- The compound most like the mobile phase in polarity will move the furthest and/or the fastest
along the stationary phase
Examples of chromatography
(4) - CORRECT ANSWER - 1. Thin layer chromatography (TLC)
- Involves the stationary phase (usually silicates, or sometimes aluminates) attached to an
aluminium plate
2. Flash/Column chromatography
- A glass tube is filled with the stationary phase (silicates and/or aluminates)
3. High pressure liquid chromatography (HPLC)
- A metal tube filled with the stationary phase and the mobile phase pumped through at high
pressure
4. Gas chromatography
- Similar stationary phase column, but the mobile phase is a gas
- These examples are widely used techniques for separating and identifying the components of
mixtures
