Chemical Analysis and Instrumental Methods

Question 1

You can identify elements and compounds using instrumental methods. What does this mean

Answer 1

Using machines

Question 2

What are the advantages of using machines? (3)

Answer 2

1) Very sensitive - can detect even the tiniest amounts of substances
2) Very fast and tests can be automated
3) Very accurate

Question 3

What can be used to ‘separate out a mixture of compounds and help you identify the substances present’?

Answer 3

Gas Chromatography

Question 4

Describe how gas chromatography works. (4)

Answer 4

1) A gas is used to carry substances through a column packed with solid material
2) The substances travel through the tube at different speeds, so they’re separated
3) The retention time can be used to identify the substance
4) The recorder draws a gas chromatograph.

Question 5

Gas Chromatography: What is the retention time?

Answer 5

The time taken to reach the detector

Question 6

Explain what the gas chromatograph shows

Answer 6

The no. of peaks show the no. of different compounds in the sample
The position of the peaks shows the retention time of each substance

Question 7

What happens after a gas chromatograph has been drawn?

Answer 7

The gas chromatography column can also be linked to a mass spectrometer. This process is know as GC-MS and can identify the substances leaving the column very accurately

Question 8

Gas Chromatography: How do you work out the relative molecular mass of each substance?

Answer 8

You can work it out from the graph that the GC-MS draws. You just read of the molecular ion peak