Topics in this chapter
- Properties of acids and bases
- Indicators and pH scale
- Reaction with metals and carbonates
- Neutralisation
- Strength and concentration
- Common salts
- Baking soda, washing soda, bleaching powder and plaster of Paris
Key learning points
✓ Acids release H⁺ ions in aqueous solution; bases release OH⁻ ions.
✓ The pH scale generally ranges from 0 to 14.
✓ A pH below 7 is acidic, 7 is neutral and above 7 is basic.
✓ Salts may be acidic, basic or neutral depending on their parent acid and base.
Important equations
Zn + 2HCl → ZnCl₂ + H₂↑Na₂CO₃ + 2HCl → 2NaCl + H₂O + CO₂HCl + NaOH → NaCl + H₂O2NaHCO₃ → Na₂CO₃ + H₂O + CO₂Multiple-choice questions
1. A solution with pH 3 is:
- Strongly basic
- Weakly basic
- Acidic
- Neutral
Answer: C — Acidic
2. The chemical name of baking soda is:
- Sodium carbonate
- Sodium hydrogen carbonate
- Calcium carbonate
- Sodium chloride
Answer: B — Sodium hydrogen carbonate
3. Plaster of Paris is prepared from:
- Gypsum
- Limestone
- Common salt
- Bleaching powder
Answer: A — Gypsum
Very short-answer questions
- What colour does blue litmus turn in an acid?
- Define neutralisation.
- Write the formula of washing soda.
Short-answer questions
- Explain the importance of pH in digestion and tooth decay.
- Describe the preparation and two uses of bleaching powder.
Long-answer question
- Discuss the chemical properties of acids and bases with balanced equations.