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🧪 Chemistry CBQ

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📝 Question 17
Chemistry Chemical Reactions ⭐ 3 Marks
Q. What happens when ethanol reacts with sodium? Write balanced equation.
✅ Detailed Solution
2C₂H₅OH + 2Na → 2C₂H₅ONa + H₂↑ Observations: • Brisk effervescence (H₂) • Sodium dissolves • Solution becomes basic Type: Substitution reaction ✓
🎓 Learning Outcomes
  • Balanced equations
  • Reaction types
  • Mechanisms
📝 Question 18
Chemistry Acids, Bases & Salts ⭐ 4 Marks
📖 Case Study
Lab Test: Pop sound is characteristic test for hydrogen gas.
Q. HCl added to zinc. Colorless gas with pop sound. Identify gas, write equation.
✅ Detailed Solution
Gas: HYDROGEN (H₂) Zn + 2HCl → ZnCl₂ + H₂↑ Pop sound confirms H₂ (Burns: 2H₂ + O₂ → 2H₂O) Type: Displacement reaction ✓
🎓 Learning Outcomes
  • Gas identification
  • Lab tests
  • Reactivity series
📝 Question 19
Chemistry Metals & Non-metals ⭐ 3 Marks
Q. Why is aluminum used for cooking utensils and electrical cables?
✅ Detailed Solution
Cooking Utensils: • Good heat conductor • Light weight • Corrosion resistant (Al₂O₃ layer) Electrical Cables: • Good electrical conductor • Light weight (less load on poles) • Cheaper than copper • Ductile ✓
🎓 Learning Outcomes
  • Properties & uses
  • Compare metals
  • Conductivity
📝 Question 20
Chemistry Carbon Compounds ⭐ 4 Marks
Q. What is homologous series? Give characteristics and first 3 alkanes.
✅ Detailed Solution
Homologous Series: Compounds with same functional group, differing by -CH₂. Characteristics: • Same general formula • Differ by -CH₂ (14 u) • Similar chemical properties Alkanes (CₙH₂ₙ₊₂): • Methane: CH₄ • Ethane: C₂H₆ • Propane: C₃H₈ ✓
🎓 Learning Outcomes
  • Define series
  • List characteristics
  • Molecular formulas
📝 Question 21
Chemistry Periodic Classification ⭐ 3 Marks
Q. Why does atomic size decrease across a period? Compare Na and Cl.
✅ Detailed Solution
Reason: Same shells, more protons → Increased nuclear charge → Electrons pulled closer Na (Period 3): 11 protons Atomic radius = 186 pm Cl (Period 3): 17 protons Atomic radius = 99 pm Na > Cl in size ✓
🎓 Learning Outcomes
  • Periodic trends
  • Compare properties
  • Electronic configuration
📝 Question 22
Chemistry Life Processes ⭐ 4 Marks
Q. Write photosynthesis equation. Why is it important for Earth?
✅ Detailed Solution
6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂ (Sunlight + Chlorophyll) Importance: 1. Food Production - Converts light to chemical energy - Base of food chains 2. Oxygen Release - Maintains 21% O₂ 3. CO₂ Removal - Controls global warming ✓
🎓 Learning Outcomes
  • Balanced equations
  • Biological importance
  • Ecology

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