Lab 2 study

If hydrogen ion concentration increases:

pH decreases

If hydrogen ion concentration decreases:

pH increases

Each step in the pH scale:

Equals a 10× (tenfold) change in hydrogen ion concentration

What is a buffer?

A buffer is a solution that resists changes in pH when small amounts of acid or base are added.

How does a buffer work?

A buffer contains:

• A weak acid and its conjugate base

• Absorbing excess H⁺ when acid is added

• Releasing H⁺ when base is added
  → This keeps pH relatively stable

Buffer used in lab:

bicarbonate buffer system (NaHCO₃ / H₂CO₃)

Molecules that can act as buffers:

• Bicarbonate (HCO₃⁻ / H₂CO₃)

• Phosphate buffers

• Proteins (like hemoglobin)

Bicarbonate buffer formula:

CO2​+H2​O↔H2​CO3​↔H++HCO3−​

Changing amounts (Law of Mass Action):

If you add more of something, the reaction shifts to reduce that change

• Add H⁺ → shifts left

• Remove H⁺ → shifts right

Effect of shifts on pH:

• Shift right → more H⁺ → pH decreases (acidic)

• Shift left → less H⁺ → pH increases (basic)

Normal blood pH:

• Normal: 7.35–7.45

• Acidosis: pH < 7.35

• Alkalosis: pH > 7.45

Vomiting

metabolic alkalosis (loss of acid)

Diarrhea

metabolic acidosis

Sprinting 1/4 mile

Metabolic acidosis (lactic acid buildup)

Hyperventilating (fear)

Respiratory alkalosis (too much CO₂ blown off)

Dyspnea (pneumonia)

Respiratory acidosis (CO₂ retained)

Hypoventilation (narcotics/alcohol)

• Respiratory acidosis (CO₂ builds up)

Compensation:

• Lungs (respiratory compensation)

  • Adjust CO₂ levels (fast)

• Kidneys (metabolic compensation)

  • Adjust H⁺ and HCO₃⁻ (slow)

NaCl + Strong Acid Why did pH change dramatically?

• NaCl is NOT a buffer

• It has:

  • No weak acid/base system to neutralize added H⁺

• So:

  • Adding acid → rapid drop in pH

NaHCO₃ + Strong Acid Why was pH change different?

• NaHCO₃ is part of a buffer system

• It:

  • Reacts with added H⁺ → forms carbonic acid

• This:

  • Slows pH change

  • Resists sudden drops in pH