Analysis of chemical equilibria is a topic covered in both undergraduate and graduate courses such as physical chemistry, chemical thermodynamics, and engineering thermodynamics. Manual calculation of problems that require a student to solve for species concentrations, partial pressures, or mole fractions usually involves the method of equilibrium constants. Exercises in homework assignments or in-class examinations are frequently limited to reactions that involve no more than four gas-phase species as the resulting arithmetic required to solve for the unknown quantity becomes too cumbersome and prone to error. Students who invest the requisite time in manually solving complex equilibrium problems in homework assignments need a tool to verify their answers. A Java Web application (“applet”) has been developed to assist chemistry students who encounter general multiphase equilibrium problems involving many species. In addition to students, chemistry educators and professional researchers will benefit from a user-friendly and free-to-use software package that can numerically compute equilibrium distributions for arbitrary reactions. The applet we present can be used to analyze complex reactions involving twenty or more species, and one such reaction, the combustion of isooctane and air, is presented as an example.