Evaluating the Heats of Combustion of Coals Using Bomb Calorimetry in the General Chemistry Laboratory

Calorimetry is a central concept in the first semester general chemistry curriculum, and constant pressure (coffee-cup) calorimetry is a common experiment in the laboratory. However, constant volume (bomb) calorimetry is traditionally reserved for the physical chemistry laboratory. This article describes the advantages of incorporating bomb calorimetry into the general chemistry laboratory by detailing an experiment on evaluating the heats of combustion of coals. Results from this experiment revealed that those coals with higher carbon contents have higher heats of combustion. The expected learning goals of this experiment and their assessment are detailed in the article. By combining coffee-cup and bomb calorimetry experiments, students gained a better understanding of closed, open, and isolated systems and were better able to discern the differences between enthalpy and internal energy. The bomb calorimetry of coals provided an excellent springboard for climate change discussions including an exploration into the types of coals, their impurities, and their formation. Students learned that it is the nitrogen and sulfur oxides, the inevitable byproducts from coal-powered electricity generation, which lead to acid rain. The connection between increasing atmospheric CO2 levels resulting from fossil fuel combustion and global climate change was explored using published data. A primary literature article on assessing the value of plastic wastes as a fuel was also incorporated into the discussion. Such discussions in the general chemistry curriculum with students from a broad spectrum of majors are critical, given the dire consequences of global climate change predicted by the 2022 Intergovernmental Panel on Climate Change (IPPCC).