An Improved Calorimeter Design for Undergraduate Isobaric Solution Calorimetry Experiments

Calorimetry is an essential part of most introductory chemistry laboratory courses, but for deployment in large enrollment laboratory classes it is often the case that compromises are necessitated through limitations of budget, apparatus suitability or chemical compatibility. Most often these will include choosing an inexpensive calorimeter such as a polystyrene coffee cup, or assuming the heat capacity of an aqueous solution is the same as that of pure water, or sometimes not experimentally measuring the calorimeter constant. To solve these problems, a new calorimeter design has been tested that employs use of a flexible polyimide resistive heater mounted to the outside of a glass beaker inserted into an inexpensive education-grade calorimeter jacket. Along with the use of other common laboratory equipment, this calorimeter is able to operate using a wide range of reagents without any chemical compatibility issues, is able to perform calibration measurements for each individual reaction mixture, is easy for students to use, and can be easily built at a fraction of the cost of commercially available isobaric calorimeters with comparable properties. This approach is also more pedagogically satisfying, as it removes many of the assumptions that students are forced to make when using other calorimeter apparatus.