Summary
Acid-base equilibria involve understanding the balance between acids and bases in a solution, characterized by the pH scale, which measures acidity or alkalinity. The Brønsted–Lowry theory defines acids as proton donors and bases as proton acceptors.
- Acid — A substance that donates hydrogen ions (H+) in a solution. Example: Hydrochloric acid (HCl) is a strong acid that completely dissociates in water.
- Base — A substance that accepts hydrogen ions (H+) in a solution. Example: Sodium hydroxide (NaOH) is a strong base that fully dissociates in water.
- pH Scale — A scale that measures the acidity or alkalinity of a solution, ranging from 0 to 14. Example: A pH of 7 is neutral, below 7 is acidic, and above 7 is alkaline.
- Neutralization Reaction — A reaction where an acid and a base react to form water and a salt. Example: HCl + NaOH → H2O + NaCl.
- Buffer Solution — A solution that resists changes in pH when small amounts of acid or base are added. Example: A mixture of ethanoic acid and sodium ethanoate acts as a buffer.
- Ka and pKa — Ka is the acid dissociation constant, and pKa is the negative logarithm of Ka, indicating acid strength. Example: A lower pKa value indicates a stronger acid.
Exam Tips
Key Definitions to Remember
- Acid: Proton donor
- Base: Proton acceptor
- pH: Measure of acidity/alkalinity
- Buffer: Solution that resists pH change
Common Confusions
- Strong vs. weak acids: Strength refers to ionization, not concentration
- pH vs. pKa: pH measures acidity, pKa indicates acid strength
Typical Exam Questions
- What is a neutralization reaction? A reaction between an acid and a base forming water and a salt.
- How do you calculate pH from [H+]? Use the formula pH = -log10 [H+].
- What is the role of a buffer solution? To maintain a stable pH when acids or bases are added.
What Examiners Usually Test
- Understanding of the pH scale and its application
- Ability to calculate pH and understand its implications
- Knowledge of acid-base reactions and buffer systems