<![CDATA[The interconnected nature of chemical concepts makes foundational understanding essential, as conceptual errors can contribute to misconceptions about more advanced topics. This study aimed to identify the prevalence and sources of misconceptions across acid–base sub-concepts among Grade XI students at SMA Negeri 10 Pekanbaru. A quantitative descriptive design was employed, involving 163 students in the 2025/2026 academic year. Data were collected using a 20-item five-tier multiple-choice diagnostic test covering five sub-concepts, supplemented by structured interviews with 15 students. The overall misconception rate was 46.29%, classified as moderate. Misconceptions were most prevalent in the ionization equilibrium constants (Ka and Kb) sub-concept (48.77%), followed by pH (47.55%), acid–base theory (46.17%), acid–base indicators (45.55%), and acid–base strength (43.40%). Personal reasoning was the most frequently identified source of misconceptions (47.3%), followed by textbooks (16.8%), teachers (14.6%), peers (13.2%), and the internet (8.2%). These findings indicate that misconceptions occurred across all five sub-concepts, with personal reasoning identified as the dominant source. The study provides a profile of acid–base misconceptions that can inform diagnostic assessment and instructional planning. It highlights the need for teachers to identify students’ conceptual difficulties and design targeted instructional strategies to strengthen understanding of acid–base chemistry.]]>
