Determination of the Chemical Activation Energy, the Rate Constant and Order of Inorganic Solid – Solid Reactions from Capillary Studies

Rabia Ahmad* and Qamer Faisal¹

Department of Chemistry, Jamia Millia Islamia, ( Central University ), Jamia Nagar, New Delhi - 110 025 (India).  

Capillary solid-solid reaction studies have been going on for many decades. These have largely been used for finding out the order of the reaction, the rate constant and for determining the activation energy. We have not come across any satisfactory justification for assigning the same meaning to these terms as in the more conventional reactions. The present work was undertaken with this in view. It is found that the terms reaction order, rate constant and the activation energy, as used and experimentally found out in capillary studies, make sense. They tell important things about a capillary reaction. However, the quantities so found out may not be directly applicable to solid-solid reactions, carried out in bulk, and more so to the same reactions occurring in solution. Capillary reactions have their own special features and are important in their own way. The above explanatory comments are based on a detailed experimental study of the two capillary reactions: CuI+HgCl2 and KI+HgCl2. These reactions have been studied in the past, but here the objective is different.

Reaction order; rate constant; activation energy; capillary solid-solid reactions