IB myp 4-5 Chemistry – Practice Questions- All Topics
Topic :IUPAC-Alcohols
Topic :IUPAC- Weightage : 21 %
All Questions for Topic : Alkanes,Alkenes,Alcohols,Carboxylic Acid,Esters,Structural Formulas
Question (8 marks) – Fuel Chemistry
Fuels produce energy when burned. Fossil fuels such as coal, oil, and natural gas supply most of the world’s energy. The reaction these fuels undergo is combustion. The outdoor lamp is used in camping and uses propane as a fuel.
a (1 mark)
Criterion A
Select the term for a reaction that releases energy.
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Answer: Exothermic
Detailed Explanation:
An exothermic reaction is one where energy is released to the surroundings, usually as heat or light. Key characteristics:
- ΔH (enthalpy change) is negative
- Common in combustion reactions like burning propane
- Energy released comes from bond formation in products (CO₂ and H₂O)
- For propane: C₃H₈ + 5O₂ → 3CO₂ + 4H₂O releases ~2220 kJ/mol
Syllabus Link:
Bonding → Energy changes in reactions
Real-world Example:
Camping stoves, car engines, power plants
b (2 marks)
Criterion A
Balance the equation for complete combustion of propane:
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Answer:
Step-by-Step Solution:
- Balance carbon atoms: 3C in propane → 3CO₂
- Balance hydrogen atoms: 8H in propane → 4H₂O (since each H₂O has 2H)
- Balance oxygen atoms:
- Products: (3×2) + (4×1) = 10 oxygen atoms
- Reactants: Need 5O₂ to provide 10 oxygen atoms
Syllabus Connection:
This demonstrates conservation of mass (Bonding → Chemical reactions) and stoichiometry (Bonding → The mole concept).
c (2 marks)
Criterion A
Propane is an alkane. Identify the family of these organic molecules:
Molecule A
Molecule B
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Answer:
- Molecule A (CH₃CH₂OH): Alcohol (ethanol)
- Molecule B (CH₃COOH): Carboxylic acid (ethanoic acid)
Functional Group Analysis:
| Compound | Functional Group | IUPAC Name |
|---|---|---|
| A | -OH (hydroxyl) | Ethanol |
| B | -COOH (carboxyl) | Ethanoic acid |
Syllabus Connection:
This tests knowledge of IUPAC nomenclature for:
- Alkanes (parent chains)
- Alcohols (-OH suffix: -ol)
- Carboxylic acids (-oic acid suffix)
d (3 marks)
Criterion A
Explain why powdered coal is preferred over solid lumps in power plants.
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Key Points:
- Powdered coal has greater surface area exposed to oxygen
- This increases the rate of combustion (reaction kinetics)
- Results in more efficient energy release
Scientific Explanation:
Surface Area Effect
- Powder: 300-2000 m²/kg surface area
- Lumps: 0.1-1 m²/kg surface area
- 1000x more reactive sites available
Collision Theory
- More frequent collisions with O₂ molecules
- Higher probability of successful reactions
- Lower effective activation energy
Power Plant Advantages:
| Benefit | Explanation |
|---|---|
| Faster combustion | Quick steam generation for turbines |
| More complete burning | Less unburned waste (↑ efficiency) |
| Better control | Easier to adjust fuel-air mixture |
Syllabus Connection:
This relates to Bonding → Reaction kinetics (factors affecting rates) and Types of chemical reaction → Combustion.