HLTH1004 W2 L2.3.2

pH and Its Significance

• Definition of pH:

  • pH is a measure of the concentration of hydrogen ions (protons) in a solution.

  • An electron can also be referred to as a proton since a hydrogen ion (H+) comprises one proton and a single negative charge.

• pH Scale:

  • The pH scale is inverted; more hydrogen ions present in a solution indicate a lower pH value.

  • Solutions with high hydrogen ion concentration (low pH) are termed acidic.

  • Neutral pH:

    • A pH of 7 represents neutrality—indicating equal concentrations of hydrogen ions and hydroxyl groups.

    • Pure water has a neutral pH of 7.

  • Basic or Alkaline Solutions:

    • Solutions with a pH above 7 are referred to as alkaline or basic.

Importance of Maintaining pH

• Human blood maintains a slightly alkaline pH, usually between 7.35 and 7.45.

• This narrow pH range is crucial because excess protons can damage chemical reactions and cell membranes.

• The body works to buffer excess acidity and maintain pH balance through various physiological processes.

Understanding the pH Scale

• As pH decreases (less than 7), acidity increases due to a higher concentration of hydrogen ions.

• Examples of pH Values:

  • Stomach acid = most acidic, with pH around 1-2.

  • Beverages like beer, vinegar, and wine exhibit moderate acidity (pH around 4-5).

  • Saliva and milk are slightly acidic to neutral.

  • Stomach acid is at the extreme acidic range, while weak acids range just below neutral.

Acids and Bases

• Acids:

  • Defined as proton donors, containing a high concentration of hydrogen ions.

  • Strong Acids:

    • Completely dissociate in solution, releasing a large amount of hydrogen ions.

• Bases or Alkalis:

  • Defined as proton acceptors—a substance that removes hydrogen ions from solution.

  • Strong Bases:

    • Also dissociate completely in solution, effectively lowering hydrogen ion concentrations.

• Weak Acids and Bases:

  • Do not fully dissociate in solution; they contribute to pH balance by interacting with spare protons.

Formation of Salts

• When an acid reacts with a base, they produce a salt.

• Salt:

  • Defined as any solute that dissociates into cations and anions other than protons and hydroxide ions.