PH

Definition

pH, or potential of hydrogen, is a measure of the acidity or basicity of a solution. It is a scale that ranges from 0 to 14, with 7 being neutral, values less than 7 being acidic, and values greater than 7 being basic or alkaline. The pH of a solution is directly related to the concentration of hydrogen ions (H+) present, and it is a critical factor in many chemical and biological processes.

5 Must Know Facts For Your Next Test

1. The pH scale is logarithmic, meaning that each unit change in pH represents a ten-fold change in the concentration of hydrogen ions.
2. The pH of a solution can be measured using a pH meter or pH test strips, which provide a quantitative assessment of the acidity or basicity.
3. The pH of a solution is a critical factor in many chemical and biological processes, such as enzyme activity, cellular function, and the solubility of compounds.
4. Acids and bases can be classified based on their strength, with strong acids and bases having a greater impact on the pH of a solution compared to weak acids and bases.
5. Buffers are solutions that resist changes in pH, and they play a crucial role in maintaining the optimal pH for various biological and chemical processes.

Review Questions

• Explain how the pH scale relates to the concentration of hydrogen ions in a solution.
  • The pH scale is a measure of the concentration of hydrogen ions (H+) in a solution. The pH value is calculated as the negative logarithm of the hydrogen ion concentration, or -log[H+]. This means that as the concentration of hydrogen ions increases, the pH value decreases, indicating a more acidic solution. Conversely, as the concentration of hydrogen ions decreases, the pH value increases, indicating a more basic or alkaline solution. The pH scale ranges from 0 to 14, with 7 being the neutral point, where the concentration of hydrogen ions and hydroxide ions (OH-) are equal.
• Describe the role of pH in the context of relative strengths of acids and bases.
  • The pH of a solution is directly related to the relative strengths of the acids and bases present. Strong acids and bases have a greater impact on the pH of a solution compared to weak acids and bases. Strong acids, such as hydrochloric acid (HCl), completely dissociate in water, producing a high concentration of hydrogen ions and a low pH. Strong bases, such as sodium hydroxide (NaOH), also completely dissociate, producing a high concentration of hydroxide ions and a high pH. Weak acids and bases, on the other hand, only partially dissociate, resulting in a more moderate impact on the pH of the solution.
• Analyze the role of pH in the hydrolysis of salts and the formation of buffers.
  • The pH of a solution is a critical factor in the hydrolysis of salts and the formation of buffers. When a salt, such as sodium acetate (CH3COONa), is dissolved in water, the salt can undergo hydrolysis, where the anion (acetate ion, CH3COO-) reacts with water to produce a weak acid (acetic acid, CH3COOH) and a weak base (sodium hydroxide, NaOH). This hydrolysis reaction can shift the pH of the solution, making it either acidic or basic, depending on the strength of the acid and base formed. Buffers, on the other hand, are solutions that resist changes in pH and are crucial for maintaining the optimal pH in various chemical and biological systems. Buffers work by providing a reserve of hydrogen ions or hydroxide ions that can neutralize added acids or bases, respectively, helping to maintain a stable pH.

Related terms

Acidity: The measure of the concentration of hydrogen ions (H+) in a solution, with lower pH values indicating higher acidity.

Basicity: The measure of the concentration of hydroxide ions (OH-) in a solution, with higher pH values indicating higher basicity or alkalinity.

Neutralization:

The process of combining an acid and a base to produce a neutral solution with a pH of 7.