All you have to do is think about the major goals of premedical science education to understand why solution chemistry is one of the most important MCAT topics. Within solution chemistry, heterogeneous solution equilibria and the solubility of weak electrolytes is a favorite subsection for the exam. Fluency with solubility product problem solving and the common ion effect are MCAT essentials. The exam often asks students to apply Le Chatelier's principle in the context of the solution process.