IGCSE Chemistry Practice Exam 2025 - Free IGCSE Chemistry Practice Questions and Study Guide

Adding a dilute acid to water before electrolysis increases the electrical conductivity of the solution. This occurs because the acid dissociates into its ions (for example, hydrogen ions and anions such as chloride or sulfate depending on the acid used), which contribute to the overall ionic strength of the solution. The presence of these charged particles enables the solution to conduct electricity more efficiently.

In an electrolysis setup, the ions in the solution move towards the electrodes, allowing electric current to pass through. Higher conductivity means that current can flow more easily, resulting in a more efficient electrolysis process. By increasing the number of ions in the solution through the addition of a dilute acid, the overall conductivity is significantly enhanced.

In contrast, other options do not accurately describe the effects of adding a dilute acid. For instance, while it might seem that increasing conductivity could somehow decrease gas production, what actually occurs is that gas production is optimized under conductive conditions, as ions more readily reach the electrodes. Additionally, the addition of acid does not inherently increase electrical resistance; rather, it decreases it because of the increased number of charge carriers. The pH of the solution is indeed influenced, but that change is secondary to the primary effect of enhancing conductivity, which is the key focus of