Chemguide: Support for CIE A level Chemistry

Learning outcomes 22.2(a) and 15.3(c)

These statements are about infra-red spectroscopy.

Before you go on, you should find and read the statement in your copy of the syllabus.

This is new for the 2016 syllabus, and there isn't a question about it in the specimen papers. So that means there won't be any evidence about what sort of questions to expect before 2016 at the earliest.

Statement 22.2(a)

You will need to work through all three pages from the infra-red spectroscopy menu.

You will find a table of absorption frequencies in the Data Book which you will have in the exam. You will find a copy towards the end of the syllabus.

Statement 15.3(c)

This statement is about the use of IR spectroscopy in detecting and measuring pollutants in the atmosphere.

You are only expected to give an outline. There is another Exam Board (OCR) which has an almost identical statement in its syllabus, and I found a question related to it. It was very simple.

All they expected was that you should recognise that IR spectroscopy identifies particular bonds in a molecule, and so each pollutant will show a different pattern of absorptions - and also that it is possible to measure the concentration of each pollutant. If you had said that, you would get two marks.

This might sound a bit vague, but it has to be. Some powerful maths and computing is going on to sort out the mixture of absorptions that you get from all the different molecules in the atmosphere.

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© Jim Clark 2014