Moles and titrations

Many teachers find quantitative analysis (ie titrations) a tough topic to teach. This may be due to the scary aspects of managing the practical work or the teaching of titration calculations, which requires a good understanding of the mole; another tough topic for both students and teachers.

A titration is simply a technique used by analytical chemists to determine the concentration of an unknown solution by reacting it with a solution of accurately known concentration.  Put like that, it sounds really easy and straightforward, so why does it cause so many teachers anxiety? Students often experience a number of difficulties when they are first introduced to titrations, from handling the equipment correctly to the ability to follow instructions (fig 1)! Some schools lack enough good quality equipment, forcing students to work in large groups. Others battle with leaky burettes, leading to meaningless results full of errors. It is easy to see how progress can be hindered.

In order to overcome some of these difficulties the topic needs to be broken down into manageable chunks. It is really important that as teachers we gradually develop the students’ skills and confidence with each of the component aspects of titrations by providing appropriate scaffolding. Being able to handle full-scale titrations in the classroom combined with the necessary calculation work requires careful planning and sequencing of ideas (see Possible teaching route – titrations).

Titrations come with potential pitfalls such as a lack of specialist equipment and students struggling to follow instructions, Dorothy Warren describes some of the difficulties with teaching this topic and shows how you can help your students to master aspects of quantitative chemistry.