"Computer Algebra in teaching chemistry: a package for balancing chemical equations." Juan Llovet, Carlos Esebbag* Departamento de Matematicas Universidad de Alcala A package prototype designed to balance chemical equations automatically is presented. The program, written in Maple V, is able to derive the charge and mass balance equations, from a non balanced chemical reaction, and solve them by means of the isolve command. As input the user introduces the reactants and the products of the reaction written in a natural chemical-like syntax. The program checks the validity of the data to verify that the mass and charge balances are possible, then it returns the balanced equation. The two main applications of the package are: - A helping tool in learning chemistry at basic level. - To teach programming in a computer algebra system to students of chemistry. In the second case, the fact that balancing of chemical equations is very well known subject for chemistry students allows the usage of the package to teach non-trivial programming techniques to this kind of students.