Flashcards
Chrome U4
Flashcards do conjunto (26)
- 1What is Chromatography?•A method of separating and analyzing mixtures.
- 2What are the chromatography techniques in U4? HPLC AND GLC•Gas Liquid Chromatography (GLC)
•High Performance Liquid Chromatography (HPLC) - 3What is the general principle in all chromatography techniques?•An eluent(mobile phase) moves past a stationary phase.
•The eluent tends to be a gas or liquid.
•Separation occurs as a result of competition to cling to the stationary phase or eluent - 4What can be said about substances which are more soluble in the eluent?•They are less soluble in the stationary phase.
- 5What is partition experiment?•Division of a soluble layer between two phases.
- 6Why is chromatography described as partitioning?•The soluble substance is divided between the eluent and stationary phase.
- 7Why do different dyes exhibit different rates of travel?•The dyes have different solubilities in both phases.
- 8What is the stationary phase in GLC?•Non volatile liquid coated onto small inert particles.
- 9How is temperature maintained in GLC?•A thermostatically controlled oven.
- 10For separation to occur within a GLC, what should be the important condition of the gas?•Sample must be either a gas.
- 11How is the injected sample carried?•By a stream of dry inert gas such as nitrogen or helium.
•The special name given to this gas is carrier gas. - 12What happens to the sample after it has left the coil?•The sample and the carrier gas pass through a detector.
- 13What is measured of the passing gas?•thermal conductivity of the passing gas
- 14What can be said about the chart produced?•A peak is shown for each component in the original mixture.
•The area shows the area under the peak is proportional to the amount of substance present. - 15For what type of liquids is GLC suitable for separating mixtures?•Volatile liquids
- 16How is identification carries out in a GLC?•Measuring the time taken for the component to reach the detector.
- 17What is the special name given to this time?•Retention time
- 18What can be said about the retention time of each component?•It is unique for each component under the same conditions
- 19What are the factors which should be constant in a GLC?•Temperature of column
•Flow rate of carrier gas
•With regards to the column, the length and diameter should be the same. - 20What is significant about the information provided by the GLC?•It is both qualitative and quantitative
- 21What does HPLC stand for?•High performance liquid chromatography
- 22What is the main difference between GLC and HPLC?•In a HPLC, the columns are shorter and eluent is a solvent rather than a gas.
- 23How are the components detected in HPLC?•By measuring UV or IR radiation.
•There is a UV spectrophotometer OR IR spectrometer attached to the end. - 24Why is the pressure in a HPLC greater than that of a GLC?•Liquids are more viscous.
•Hence, more pressure is needed to make the liquids pass through. - 25What is the output of the HPLC?•A series of peak which are similar to that of a GLC
- 26Apart from making the solvent move, why is increased pressure so important?•Since the pressure increases the speed of the eluent, the extent to which the band of the component undergoes diffusion is less.
•Since less diffusion occurs, HPLC has a high resolution. Therefore, it is more accurate.
Informações
- Descrição
- A-Level Chemistry FlashCards sobre Chrome U4, criado por Jio Jenassi em 09-06-2016.
- Criado por
- Jio Jenassi · jun 2016
- Atualizado
- 16 jun 2016
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