A web-based course was developed in order to improve pre-service teachers’ knowledge concerning complexation and masking in analytical chemistry. This course was designed to enhance students’ achievement by promoting individual and student-centered learning through the use of a series of web-based modules in the subject area. A chemistry achievement test of 10 questions was developed and administered as a pre-test to assess student knowledge in the general area of complexation and masking. Eighty-four students were randomly divided into two groups. One group, eferred to hereafter as the experimental group, learned about the specified material within the Web-based course that was developed for this study. The control group was traditionally taught using a lecture format. The increase in the achievement of the control and experimental groups was then assessed through the dministration of the chemistry achievement test of 10 questions which was used as a post-test. Significant differences in group achievement scores, favoring the experimental group, were observed between the post-test achievement averages of the control group and the treatment group.