Two of the most exemplary capabilities of the human mind are the capability of using perceptions (human knowledge) in purposeful ways and the capability of approximating perceptions by statements in natural language.There are many chemical reactions that are very sensitive and a little change in temperature and particle size can create serious problems. We have developed the idea of Approximate Reasoning and Fuzzy Logic to find the approximate value of reaction rate with the given conditions by means of the extended modus ponens law. The methodology is very simple and can be applied to several other chemical reactions in the similar way by connecting AND and OR operations.