Last month’s post focused on the mandatory lab covered in section 1.2, ‘The obtaining and use of experimental data for deriving empirical formulas from reactions involving mass changes’.
This month, I thought I would carry on with this theme and focus on the second mandatory lab found in topic 1.3, namely ‘use of the experimental method of titration to calculate the concentration of a solution by reference to a standard solution’.
Personally, I think titrations form the nuts and bolts of the chemistry practical course as they are such useful, straight forwards and relatively cheap analytical instruments we have available to us in schools and I was very pleased to see that the IB had included titrations in the list of mandatory labs.
As I wrote previously, it goes without saying that you, the teacher are fully responsible for ensuring these labs are carries out safely and it is imperative that you carry out the appropriate risk assessments before engaging in any of the labs listed.
Incidentally, two very good videos are posted on YouTube regarding titrations:
The first is how to make a standard solution:
And the second is how to carry out a titration:
So what types of labs can you investigate:
Here are a few ideas – some, I am sure you will have heard of and will have carried out, others I hope will be new to you and will stimulate some research and interesting new experiments for your students.
An introductory titration could involve using some dilute NaOH and HCl with Phenolphatlein (sp) indicator.
Or how about finding the amount of calcium carbonate in an egg shell by reacting HCl from the burette with an egg shell. A solid titration if there is such a thing – good for beginners as well as there is no pipetting.
Redox titrations are always good – how much Fe2+ is there in an iron tablet – this uses MnO4- as the oxidizing agent and indicator.
A similar titration can be done with H2O2 and MnO4– . This lab could be used to determine the vol of a H2O2 solution.
And finally, a new one to me, the percentage of Cl– in salt. The titration involves using silver nitrate in the conical flask and a salt solution in the burette (Click here for more information.)
As ever, it would be really nice if you could share any other titrations you may have carried out with your classes that are not listed here. I would love to read about them.
Next month, I intend looking at mandatory lab 1.3, ‘obtaining and the use of experimental values to calculate the molar mass of a gas from the ideal gas equation’.