Abstract. The subject of this article is the service-oriented architecture utilization in the design and implementation of a web service that is intended to perform selected thermochemical calculations for chemical reactions. Computing functions allow the chemical reaction calculations, such as molar heat capacity, enthalpy, entropy and Gibbs free energy. In the next part, there is a description of each function, the method of service calling in the client application and the structure specification of outputs and error states of the service. In addition to computing functions, the web service also has a group of three information functions that characterize the purpose of the web service and its parameters, provide in tabular form a list of all web service functions and a list of all error states of the web service. The final section describes the presentation web service application with a demonstration of the specific calculations, the possibilities of using the service, and a further solution treatment.