In what context could students use this titration?

The most common context would be the determination of 'hardness' in water, which is caused by dissolved calcium and magnesium ions. 

Could the experiment be developed further?

Yes. The direct titration of tap water with edta enables students to work out a value for the total hardness of water. If they boil the solution for some time then titrate a sample after it has cooled down they can find a value for the permanent hardness in the water. The temporary hardness can be found by subtracting the permanent hardness from the total hardness.

Is the titration straightforward to do?

Some students find the colour change a little dificult to judge and will need to practise until they become confident that they can detect the end point accurately.

Are there any other issues I should be aware of?

An edta solution is normally made up using its disodium salt. It is somewhat difficult to get it to dissolve in water. The trick is to make sure that the pH is around 8 by adding sodium hydroxide solution. When the solid has completely dissolved the solution can be made up to the required volume.

Do we make use of inorganic complexes in any other form of analysis?

Yes. Many metal ion complexes are coloured. The intensity of the colour of a solution containing the complex ion depends on the concentration of the complex and therefore on the concentration of the metal ion. We can use a colorimeter to measure how much light the solution absorbs and so find out the concentration of the metal ion.

Can you give another example of a complex used in analysis?

Fe³⁺ ions form a blood red coloured complex with thiocyanate ions. We can measure the absorption of a solution to determine the concentration of Fe³⁺ ions in it. The same experiment is used to check that the thiocyanate ion concentration of waste water from steel works is within legal limits before it is discharged into a river. You can find out more about this experiment by subscribing to the Analytical chemistry course.