Qualitative Analysis

What are my objectives while studying this topic?


By studying this topic you’ll use qualitative analysis to detect cations and anions in a sample compound. You will learn how to identify the different ions using several tests and use the information to find out what an unknown compound is.


Why is this important?


Qualitative analysis is very important in labatories in order for scientists to identify certain compounds from different tests. It’s not something that tells you how much of a chemical you’ve got, it’s a series of procedures or tests that can tell you what a chemical is. For example - What makes fireworks colourful?

Is it possible to find out what chemicals are in a firework? It’s the metal ions in the compounds that are in them – different metal ions give different colours in a flame. You can use this phenomenon to find out what metal is in a compound. There are also lots of chemical tests that can be done to find out what else is in the compound.


Who uses these techniques?


So, who uses all these analytical techniques you've been studying? There are many companies that use Analytical Science. Some companies make chemicals and have to analyse their quality. Other companies, such as hospitals labs, analyse samples obtained from other sources.


In this section, you will research two different companies that use analytical science. You will have to explain what type of work they do, the jobs that their staff carry out and the types of legal constraints that the company has to follow and adhere to.


The quality of your writing is very important here so it would be useful if you could research two very different types of companies. For example, a large and small company or one that is profit making and one that is not.


Can I get an introduction to this topic?


Yes, why not have a look at the following clip:


What will I be expected to be able to do after studying this topic?


  • Explain the different ways in which qualitative analysis can be used to analyse inorganic chemicals

  • Report on one qualitative analysis that you have carried out. This report must give details of:

  • The risk assessment undertaken before carrying out your qualitative analysis

  • The standard procedure used to carry out chemical tests to identify cations and anions in an inorganic compound

  • Analysis and interpretation of results

  • A detailed evaluation of the analysis including how well the tests were carried out and the reasons for using these particular tests


What are the key words to learn and use?


  • cation

  • anion

  • flame test

  • halide ions

  • metal ions

  • sulphates

  • carbonates

  • solubility


How long will this topic take to study?


On average you’ll be looking at about seven hours of study time.


What are the main activities on this topic?


Before you get started, have a go at matching the ions below to their symbols - you’ll get better marks if you use symbols and formulae in your write-up:


Na+

Carbonate

K+

Lead(II)

Ca2+

Bromide

Fe2+

Sodium

Li+

Potassium

Fe3+

Chloride

Cu2+

Iron(II)

Cl-

Sulphate

SO42-

Barium

Ba2+

Iron(III)

CO32-

Copper(II)

Br-

Lithium

Pb2+

Calcium


Experiment!


Research the different types of qualitative tests that can be used for ion identification.



You should carry out the tests for the following ions:


  • Sodium

  • Potassium

  • Lithium

  • Calcium

  • Copper(II)

  • Lead

  • Barium

  • Iron(II)

  • Iron(III)

  • Chloride

  • Bromide

  • Carbonate

  • Sulphate


Make sure you are aware of the standard procedures used to check the results you got for each ion. You should then check whether these results are right by doing further research on what the tests really do show.


You will then be given some unknown compounds by your teacher. You should then carry out the tests you did before on these compounds. By comparing the results with those that you know, you should be able to identify them.


Portfolio Activity


Write these experiments up for submission. You could use the following writing frame to do this:



You should include the standard procedures used for your initial tests, including all the results you got and then the results of your investigation into the unknown compounds. You should also try and include the following;


  • Research on ion identification

  • Risk Assessment

  • Tabulation of Results

  • Interpretation & Conclusions


Part of your assessment requires you to use other people’s work, such as adapting standard procedures or finding out and using information on the internet. For example, finding out what the results of the tests really are. When you use information like this you need to reference it properly in your reports. The following link takes you to a suitable method for referencing:



Back to Top