This research study was conducted to investigate the interactions of specific student aptitudes with their ability to solve chemistry problems of varying structure and information. Fourteen classroom quizzes were validated and a number of in-task variables were identified for analysis. These variables included: the nature of information given (implicit or explicit); the type of information provided in the questions (relevant or irrelevant); the algebraic format required to solve the problems; and the ability/inability to demonstrate reversibilities, negation, and reciprocity. Results (based on responses of 77 high school chemistry students) indicate: (1) that field independent students were significantly better at solving proportional reasoning problems containing relevant and irrelevant information and/or implicit information than field dependent students; (2) that the degree of formal reasoning and proportional reasoning were significantly correlated with success in chemistry, independent of item in-task conditions; (3) a significant difference between the sexes favoring males on the ability to solve proportional reasoning problems; and (4) no significant interactions between sex and chemistry achievement. (Author/JN)