Kinetic Explorations of the Candy–Cola Soda Geyser

Protocols for examining the kinetics of CO2 escape from solution during the popular Diet Coke and Mentos experiment have been explored. The methods developed allow teachers to demonstrate and students to explore various physicochemical processes involved when Mentos candies are placed in Diet Coke. For example, a pH meter can be used to observe a slight decrease in acidity as dissolved CO2 escapes the soda. Furthermore, a balance or CO2 sensor can be used to directly measure CO2 escape. Arrhenius analysis of degassing rates determined using these latter methods yielded an activation energy of 25 kJ mol–1 for the conversion of CO2(aq) to CO2(g). The materials required for the experiments are easy to acquire and set up; therefore these investigations are amenable for use in high school and undergraduate chemistry classrooms and laboratories