Acid Test 1 Copyright © 2026 Pearson Education, Inc. Acid Test A water quality laboratory focuses on monitoring the impact of acid rain on local lakes. Acidity is measured using the pH scale, which operates on the logarithm of the hydrogen ion concentration in water, where a higher concentration of hydrogen ions makes a solution more acidic. Accurate measurements are important because even a slight decrease in pH indicates a significant increase in acidity. For example, a lake sample showing a hydrogen ion concentration of 0.0001 moles per liter has a pH of 4. This level of acidity suggests that the lake is moderately acidic, possibly harming fish and other aquatic life and showing that the ecosystem is under stress. Recognizing the logarithmic relationship in pH values enables scientists to better evaluate environmental changes and guide effective policy decisions. This relationship between hydrogen ion concentration and pH allows for precise calculations of acidity levels in lake water. pH can be calculated using the negative logarithm of the concentration of hydrogen ions: pH = –log[H+] [H+] is the concentration of hydrogen ions in moles per liter. 1. For each of these concentrations, determine the pH, rounded to the nearest tenth. Discuss with a partner how a change in concentration affects the pH. a. 0.01 moles per liter b. 0.05 moles per liter c. 0.0001 moles per liter 2. How many times more concentrated is an acid with a pH of 3 than another acid with each of these pH measurements? a. pH 4 b. pH 7 3. Consider the formula: pH = –log[H+]. a. If the pH of a lake is 5, what is the hydrogen concentration? b. If another lake has 100 times more [H+], what is its pH?
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