Summary
Acids are substances that produce H+ ions in aqueous solutions, while bases produce OH- ions. The pH scale measures the acidity or alkalinity of a solution, with pH 7 being neutral, less than 7 acidic, and greater than 7 alkaline.
- Acid — A substance that donates protons (H+ ions) in a solution. Example: Hydrochloric acid (HCl) dissociates in water to release H+ ions.
- Base — A substance that accepts protons (H+ ions) in a solution. Example: Sodium hydroxide (NaOH) dissociates in water to release OH- ions.
- Strong Acid — Completely dissociates in aqueous solution. Example: Sulfuric acid (H2SO4) fully dissociates in water.
- Weak Acid — Partially dissociates in aqueous solution. Example: Ethanoic acid (CH3COOH) partially dissociates in water.
- Strong Base — Fully dissociates in aqueous solution to release OH- ions. Example: Sodium hydroxide (NaOH).
- Weak Base — Partially dissociates in aqueous solution to release OH- ions. Example: Ammonia (NH3).
Exam Tips
Key Definitions to Remember
- Acids produce H+ ions in aqueous solutions.
- Bases produce OH- ions in aqueous solutions.
- Strong acids completely dissociate in water.
- Weak acids partially dissociate in water.
Common Confusions
- Strong vs. concentrated: Strong refers to complete dissociation, while concentrated refers to the amount of substance.
- Weak vs. dilute: Weak refers to partial dissociation, while dilute refers to the amount of substance.
Typical Exam Questions
- What happens to red litmus paper in an acidic solution? It stays red.
- What is produced when an acid reacts with a metal? Salt and hydrogen gas.
- How can you test for hydrogen gas? It burns with a squeaky pop when a burning splint is held near.
What Examiners Usually Test
- Understanding of the pH scale and its implications.
- Ability to write balanced chemical equations for reactions involving acids and bases.
- Differences between strong and weak acids and bases.