Fragmented Conceptual Understanding and Quantitative Challenges in Stoichiometry and Chemical Reactions among Grade 12 Students

Abstract

This study investigated the conceptual understanding of stoichiometry and chemical reactions among Grade 12 senior high school learners and developed a standardized diagnostic questionnaire to identify least mastered competencies. Employing a descriptive research design with an instrument development and survey approach, the study involved seventy four (74) Grade 12 learners from a public senior high school for the main assessment, while pilot testing was conducted with one hundred fifty (150) learners from two other schools to establish the instrument’s reliability and validity. Data were analyzed using descriptive statistics and item analysis to determine mastery levels across selected chemistry competencies aligned with the K–12 Most Essential Learning Competencies (MELCs). Results indicated generally low mastery, with a Mean Percentage Score (MPS) of 54.86, classified as not mastered. Learners exhibited the greatest difficulty with quantitatively oriented competencies, including determining molar mass and calculating mass, moles, and number of particles. Other least mastered competencies included identifying types of chemical reactions, writing balanced chemical equations using the Law of Conservation of Mass, and explaining the mole concept. Conversely, learners demonstrated relatively better performance in recognizing chemical reactions in environmental and biological contexts, suggesting stronger familiarity with observable phenomena than with abstract or mathematical concepts. The findings reveal fragmented conceptual understanding and limited integration of quantitative reasoning in senior high school chemistry learning. The validated diagnostic questionnaire provides a practical tool for identifying learners’ conceptual gaps and informing targeted instructional interventions. These results underscore the need for teaching strategies that enhance conceptual clarity, quantitative problem-solving, and real-world application of stoichiometry and chemical reactions.