Instrumental Techniques

Question 1

principle of chromatography

Answer 1

separation of a mixture of components occurs as a result of select adsorbance of the components of the mixture on a stationary phase while being carried by a mobile phase

Question 2

principle of gas chromotography

Answer 2

a gaseous mobile phase is in contact with a stationary phase and separation of the mixture occurs as a result of selective adsorbance of the components of the mixture on the stationary phase

Question 3

principle of high performance liquid chromatography

Answer 3

mobile phase is in contact with a stationary phase which is fine particles of a solid and separation of a mixture occurs as a result of selective adsorbance of the components of the mixture on the stationary phase

Question 4

principle of infa-red spectroscopy

Answer 4

organic compounds adsorb infa red radiation of certain frequencies the combination of frequencies that are absorbed by the sample depend on the bonding within the molecule and are unique that particular molecule

Question 5

principle of ultra violet spectrometry

Answer 5

absorbance is directly proportional to the concentration of the substance

Question 6

what is the function of paper gas and HPLC chromatography

Answer 6

to separate substances in a mixture and to help identify the substances in the sample

Question 7

what are IR and UV spectroscopy used for

Answer 7

identify substances

Question 8

how do we identify the purity of a substance?

Answer 8

melting point determination gives a good idea of the purity of a substance
if a substance IS PURE it will melt at one temperature
if a substance is IMPURE it will melt at a lower temperature than expected and over a range of temperatures

Question 9

stationary phase of paper chromatography

Answer 9

paper

Question 10

mobile phase of paper chromatography

Answer 10

solvent

Question 11

why do we have to use a pencil to draw the line in paper chromatography

Answer 11

pencil is insoluble

Question 12

where is the most soluble substance on paper chromatography

Answer 12

at the top of the paper far from the solvent

Question 13

where is the least soluble substance on paper chromatography

Answer 13

nearest to the pencil line

Question 14

stationary phase of gas chromatography

Answer 14

non volatile liquid on silica or alumina particles

Question 15

mobile phase of gas chromatography

Answer 15

carrier gas ie N2 /He /Ar

Question 16

give a brief description of gas chromatography

Answer 16

sample is injected onto the hot GC column and vaporises
carrier gas pushes the sample through the column
the components in the mixture adsorb onto the stationary phase
the longer the substance spends on the column the greater the affinity that substance has for the liquid
the substances emerge from the column and pass through a detector

Question 17

use for gas chromatography

Answer 17

measures the level of alcohol in blood
drug testing for athletes

Question 18

give a brief description of paper chromatography

Answer 18

spot substance on a pencil line 1cm away from the bottom of the paper, place in solvent
as the solvent travels up the paper, the different substances in the spot dissolve in the solvent and travel up the paper wit the solvent
different substanes have different soluablility in the solvent

Question 19

stationary phase in HPLC

Answer 19

fine silica particles

Question 20

mobile phase in HPLC

Answer 20

liquid solvent

Question 21

give a brief description of HPLC

Answer 21

pump is used to force substances through the column
inject the sample into the column and the liquid solvent carries the substance through the column. the substances adsorb onto the silica particles with a detector on the other end

Question 22

use of HPLC

Answer 22

determine concentration of alcohol in blood

Question 23

advantages of HPLC of gas chromatography

Answer 23

HPLC is carried out at a lower temperature so substances that could decompose at higher temperatures can be analysed

HPLC is more efficient- column is shorter which gives faster results

HPLC is suited for analysis of non volatile mixtures.

Question 24

give a brief description of IR spectroscopy

Answer 24

IR radiation is passed through the sample and organic compounds absorb IR radiation of fixed frequencies
the radiation is absorbed by the vibrations of the bonds in the molecule
every organic molecule has a unique IR spectrum that acts like a finger print for the molecule

Question 25

use of IR spectroscopy

Answer 25

used to identify functional groups in a molecule

Question 26

is UV spectroscopy qualative or quantative

Answer 26

quantative

Question 27

give a brief description of UV spectroscopy

Answer 27

shine UV light on sample
detector measures of much light has been absorbed by the sample
the amount of light absorbed is directly proportional to the concentration of the sample