Water Nuggets Practice Exam

When carbon dioxide (CO2) is added to water, it undergoes a chemical reaction to form carbonic acid (H2CO3). This acid dissociates partially in water, releasing hydrogen ions (H+). The release of these hydrogen ions increases the concentration of H+ in the solution, which leads to a decrease in pH. A low pH indicates a more acidic solution, so the action of adding CO2 effectively lowers the pH of the water. The understanding of how pH is measured is crucial here; pH is a logarithmic scale that reflects the concentration of hydrogen ions in a solution. As the concentration of H+ ions increases due to the formation of carbonic acid from dissolved CO2, the pH value decreases, indicating a more acidic environment. The other options do not align with this chemical understanding. Increasing pH would imply a more basic solution, which occurs when acids are neutralized or removed, rather than when CO2 is added. Changing the color of the water or having no noticeable change does not occur as a result of CO2 addition, as its primary effect is on the acidity of the solution.