This article describes an experiment using a novel gasometric assembly to determine the thickness and number of atomic layers of zinc coating on galvanized iron substrates. Students solved this problem through three stages. In the first stage, students were encouraged to find a suitable acidic concentration through the guided-inquiry approach. In the second stage, students performed a procedure using a gasometric device associated with data processing. In the third stage, students were provided hints to answer the number of atomic layers of zinc coating through guided problem solving. This experiment is an interesting challenge for undergraduate chemistry students. Student learning is diversified according to various concepts, laws, techniques, and skills. The concepts include vapor pressure, atmospheric pressure, and atomic packing structure. The laws include Dalton's law of partial pressures and ideal gas law. The techniques include the vernier caliper and barometer and assembling a novel gasometric device. Skills require significant figure operation, cone surface-area calculation, data processing, the inquiry-based approach, and problem solving. Students' results showed that a galvanized iron wire and two galvanized nails have 23800-29200, 14600-17900, and 5300-6490 atomic layers of zinc coating, respectively. Statistical analyses of students' and instructor's data indicated that this experiment is suitable for a second-semester general chemistry laboratory. (Contains 1 figure and 3 tables.)