Chapter 2 - Section 2.2 - Study Guide - Assess Your Learning Outcomes - Page 74: 5

**pH (potential of hydrogen)** is a measure of the acidity or basicity of a solution. It is mathematically defined as the negative logarithm (base 10) of the concentration of hydrogen ions ([H+]) in a solution. The pH scale is a numerical scale that ranges from 0 to 14, with lower numbers indicating acidity, higher numbers indicating alkalinity (basicity), and 7 being neutral. Mathematically, pH is defined as: **pH = -log[H+]** Here's a breakdown of the pH scale and the meanings of acid and base: **pH Scale:** - **pH 0-6:** Solutions with pH values between 0 and 6 are considered acidic. Lower pH values indicate stronger acidity, with pH 0 being the most acidic. - **pH 7:** A pH of 7 is considered neutral. This means that the concentration of hydrogen ions ([H+]) is equal to the concentration of hydroxide ions ([OH-]), resulting in a balanced, neither acidic nor basic, solution. - **pH 8-14:** Solutions with pH values between 8 and 14 are considered basic or alkaline. Higher pH values indicate stronger alkalinity, with pH 14 being the most basic. **Meanings of Acid and Base:** - **Acid:** An acid is a substance that, when dissolved in water, increases the concentration of hydrogen ions ([H+]) in the solution. Acids typically have a pH less than 7. Examples of common acids include hydrochloric acid (HCl), sulfuric acid (H2SO4), and citric acid found in citrus fruits. - **Base (Alkali):** A base is a substance that, when dissolved in water, increases the concentration of hydroxide ions ([OH-]) in the solution. Bases typically have a pH greater than 7. Examples of common bases include sodium hydroxide (NaOH), potassium hydroxide (KOH), and ammonia (NH3). The pH scale is crucial in chemistry and biology because it helps quantify the level of acidity or alkalinity of solutions. Many chemical reactions, especially enzyme-catalyzed reactions in biological systems, are sensitive to pH. Maintaining the proper pH in various biological environments, such as the bloodstream or cellular compartments, is vital for the proper functioning of biological processes. In summary, pH is a measure of acidity or basicity defined as the negative logarithm of the hydrogen ion concentration ([H+]) in a solution. The pH scale ranges from 0 to 14, with lower values representing acidity, higher values representing alkalinity, and 7 representing neutrality. Acids increase [H+] in a solution, while bases increase [OH-]. Understanding pH is essential in chemistry and biology for assessing and controlling the properties of solutions and their impact on chemical and biological processes.

**pH (potential of hydrogen)** is a measure of the acidity or basicity of a solution. It is mathematically defined as the negative logarithm (base 10) of the concentration of hydrogen ions ([H+]) in a solution. The pH scale is a numerical scale that ranges from 0 to 14, with lower numbers indicating acidity, higher numbers indicating alkalinity (basicity), and 7 being neutral. Mathematically, pH is defined as: **pH = -log[H+]** Here's a breakdown of the pH scale and the meanings of acid and base: **pH Scale:** - **pH 0-6:** Solutions with pH values between 0 and 6 are considered acidic. Lower pH values indicate stronger acidity, with pH 0 being the most acidic. - **pH 7:** A pH of 7 is considered neutral. This means that the concentration of hydrogen ions ([H+]) is equal to the concentration of hydroxide ions ([OH-]), resulting in a balanced, neither acidic nor basic, solution. - **pH 8-14:** Solutions with pH values between 8 and 14 are considered basic or alkaline. Higher pH values indicate stronger alkalinity, with pH 14 being the most basic. **Meanings of Acid and Base:** - **Acid:** An acid is a substance that, when dissolved in water, increases the concentration of hydrogen ions ([H+]) in the solution. Acids typically have a pH less than 7. Examples of common acids include hydrochloric acid (HCl), sulfuric acid (H2SO4), and citric acid found in citrus fruits. - **Base (Alkali):** A base is a substance that, when dissolved in water, increases the concentration of hydroxide ions ([OH-]) in the solution. Bases typically have a pH greater than 7. Examples of common bases include sodium hydroxide (NaOH), potassium hydroxide (KOH), and ammonia (NH3). The pH scale is crucial in chemistry and biology because it helps quantify the level of acidity or alkalinity of solutions. Many chemical reactions, especially enzyme-catalyzed reactions in biological systems, are sensitive to pH. Maintaining the proper pH in various biological environments, such as the bloodstream or cellular compartments, is vital for the proper functioning of biological processes. In summary, pH is a measure of acidity or basicity defined as the negative logarithm of the hydrogen ion concentration ([H+]) in a solution. The pH scale ranges from 0 to 14, with lower values representing acidity, higher values representing alkalinity, and 7 representing neutrality. Acids increase [H+] in a solution, while bases increase [OH-]. Understanding pH is essential in chemistry and biology for assessing and controlling the properties of solutions and their impact on chemical and biological processes.