Overview
This lecture explains the concepts of acids, bases, the pH scale, and introduces buffers and their importance in biological systems.
pH and Its Meaning
- pH indicates the concentration of hydrogen ions (H+) in a solution.
- Written as a lowercase "p" and uppercase "H" (pH).
- Water ionizes into hydrogen ions (H+) and hydroxide ions (OH-).
Acids and Bases Defined
- Acids have a pH range from 1.0 to 6.9.
- Bases have a pH range from 7.1 to 14.0.
- Pure water has a neutral pH of 7.0.
- Acids are sour, and bases are bitter in taste.
Strength of Acids and Bases
- The further from pH 7, the stronger the acid or base.
- pH of 2 is a strong acid; pH of 8 is a weak base.
- Formulas for acids start with H+ and release hydrogen ions in water.
- The more H+ ions released, the stronger the acid.
- Formulas for bases end with OH- and release hydroxide ions in water.
Examples of Acids and Bases
- Examples of acids: hydrochloric acid, hydrobromic acid, phosphoric acid.
- Examples of bases: lithium hydroxide, potassium hydroxide, sodium hydroxide.
- Students are not required to memorize these formulas.
Buffers and Biological Importance
- Buffers are chemicals that help maintain a stable pH.
- Human blood has a pH of about 7.4, which is a weak base.
- Drastic changes in blood pH can cause harm, so buffers stabilize it.
- If body pH cannot be regulated, serious health issues may occur.
Key Terms & Definitions
- pH — a measure of hydrogen ion concentration in a solution.
- Acid — a substance that releases hydrogen ions (H+) in water (pH 1.0–6.9).
- Base — a substance that releases hydroxide ions (OH-) in water (pH 7.1–14.0).
- Buffer — a chemical that keeps pH within a narrow range.
Action Items / Next Steps
- Re-watch any video segments as needed.
- Email the instructor with questions.
- Review and understand the pH scale and buffer function.