Chemistry · MU Pleven

Strength of acids and bases – pKa and pKb. Henderson–Hasselbalch equation. Buffers.

Covers acid and base strength through pKa and pKb, and the Henderson–Hasselbalch equation for acidic and basic buffers, with their pH ranges and example pairs. Goes on to buffer capacity, including the formula and the condition for maximum capacity when salt and acid concentrations are equal. Ends with the three blood buffer systems, the normal blood pH range, and the metabolic and respiratory causes of acidosis and alkalosis.

Inside: 3 sections · 3 labelled pictures · 5 formulas · 22 flashcards · 3 min

Topic 17 of 47 in the MU Pleven syllabus for Chemistry (Medicine, Year 1). The free AceMed note covers it in 3 sections, about 391 words (3 min of reading), with 22 flashcards.

In this note

  1. Strength of acids and bases – pKa and pKb. Henderson–Hasselbalch equation. Buffers.
  2. Buffer capacity
  3. Buffers in blood

Strength of acids and bases – pKa and pKb. Henderson–Hasselbalch equation. Buffers.

Equal to the mols of strong acid/strong base added to 1l buffer solution that would change its pH with 1 unit.

A solution that can resist a change in pH when small amounts of acid/base are added.

Acidic buffer: Weak acid + conjugate salt = acidic buffer solution pH < 7 (CH3COOH + CH3COONa)

Basic buffer: Weak base + conjugate salt = alkaline buffer solution pH > 7 (NH3 + NH4Cl)

The Henderson-Hesselbach equation

pH acidic buffer = pKa + (log (concentration of salt) / (concentration of acid))

pH basic buffer = 14 - pKb + (log (concentration of base) / (concentration of salt))

Acidic/Basic buffer solutions

[A^-] - Molar concentration of acid's conjugate base

[HA] - Molar concentration of weak acid

Buffer capacity

Amount of strong acid or base required to change the pH of a solution by 1 unit.

Equal to the mols of strong acid/strong base added to 1l buffer solution that would change its pH with 1 unit.

-Grams of strong acid/base required to change the pH of 1 litre

-Change in pH

In order to reach the max buffer capacity: increase the concentration of the the strong acid/ strong base. pH buffer = pKa. Cs = Ca

Continue reading free

The whole note, all 3 sections, is free with an AceMed account, with its 22 flashcards. Premium adds flashcard recall, highlights and Ask AI.

Start freeAlready a member? Open the note