3. A survey of animal life in a pond suggests that a native fish species no longer inhabits the pond. The biologist leading the survey hypothesizes that the pond has been made more acidic by acid precipitation. She thinks that this acidity has made the pond uninhabitable by this fish species. The biologist has enlisted a chemist to help her analyze the situation and decide whether her hypothesis is supportable. What is the first chemical test the chemist should perform to help the biologist test her hypothesis?