Lecture Notes: Acids, Bases, pH, and Buffers

Water Molecule Dissociation

Water molecules in a cup don't always exist as H2O due to dissociation.
Hydrogen Atom Shift: A hydrogen atom can shift from one water molecule to another.
- Leaves as a proton (H+), forming a hydronium ion (H3O+).
- The remaining part is a hydroxide ion (OH-).
Simplified Reaction: H2O → H+ + OH- (ignoring the other water molecule in practice).
Dynamic Equilibrium: Water molecules dissociate and reform at a tiny rate (1 in 500 million).

Importance of Ion Concentration

Balance of Ions: Concentration of H+ and OH- is crucial in cell chemistry.
In pure water, concentrations of H+ and OH- are equal, making it neutral.

Acids and Bases

Acids: Increase H+ concentration.
Bases: Decrease H+ concentration, resulting in increased OH-.

pH Scale

Definition: pH is the negative logarithm of H+ concentration.
- pH = -log[H+]
Neutral Solution: pH of 7 (H+ = OH- = 10^-7 M).
Acidic Solution: pH < 7 (High H+ concentration).
Basic Solution: pH > 7 (Low H+ concentration).

Logarithmic Nature of pH Scale

Scale Range: 0 to 14.
Logarithmic Base 10: Each pH unit indicates a tenfold change in H+ concentration.
- Example: pH 6 has 10x more H+ than pH 7.
- Example: pH 13 has 1000x less H+ than pH 10.

Buffers

Function: Minimize changes in H+ and OH- concentrations.
Composition: Typically contain a weak acid and its corresponding base.
- Can absorb or release H+ to maintain stable pH.
Relevance: Keep biological fluids (e.g., blood) close to neutral pH.

These notes outline the key concepts of acids, bases, pH, and buffers as explained in the lecture. Focus on understanding the dynamics of water dissociation, the importance of ion concentrations, and how pH is measured and maintained in biological systems.