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3.2.4Organic Chemistry

Reducing Pollution — Edexcel AS Chemistry Revision Notes & Topical Questions

5 min read 5 parts Lesson 22 of 42

📚 Edexcel AS Chemistry Hub / Topical Revision
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Curriculum Equation Key معادلة تفاعل تكوين الإستر (الأسترة) - Esterification Reaction EquationFast Exam Solution
R-COOH + R2-OH ⇌ (conc. H₂SO₄) R-COO-R2 + H₂O
Word Equation & Conditions: حمض كربوكسيلي + كحول (في وجود حمض الكبريتيك المركز كعامل حفاز ونازع للماء) ⇌ إستر + ماء
Location & Specifications: الكيمياء العضوية للثانوية العامة والتحصيلي و Edexcel Chemistry.
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Part 1 of 5Catalytic Converters

Structure
  • Structure A ceramic honeycomb coated with platinum, palladium and rhodium gives a large surface area in the exhaust.
Reaction 1
  • Reaction 1 Carbon monoxide and nitrogen monoxide react: 2CO + 2NO → 2CO₂ + N₂.
Reaction 2
  • Reaction 2 Unburnt hydrocarbons are oxidised, for example 2C₈H₁₈ + 50NO → 16CO₂ + 18H₂O + 25N₂.
Result
  • Result Three harmful gases are converted into carbon dioxide, water and nitrogen, which is far less harmful.
Limitations
  • Limitations The catalyst is expensive, works only once hot, and is poisoned by lead and sulfur.

Part 2 of 5Removing Sulfur Dioxide

1
Sulfur can be removed from fuel before burning, which lowers the amount of SO₂ formed.
2
In power stations, flue gases containing SO₂ are passed through a slurry of calcium oxide or calcium carbonate.
3
The SO₂ reacts as an acidic oxide: CaO + SO₂ → CaSO₃.
4
Calcium carbonate works too: CaCO₃ + SO₂ → CaSO₃ + CO₂.
5
The calcium sulfite can be oxidised to calcium sulfate (gypsum), which is sold for plasterboard.

Part 3 of 5Other Approaches

Other Approaches
Lower temperature
  • Lower temperature Lowering the combustion temperature in engines reduces the amount of nitrogen oxides formed from air.
Biofuels
  • Biofuels Biofuels absorb CO₂ as the plants grow, so they are close to carbon neutral overall.
Efficiency
  • Efficiency Engines that burn fuel more efficiently produce less CO and less unburnt hydrocarbon.
Regulation
  • Regulation Laws that set emission limits drive the adoption of cleaner technology.
Alternatives
  • Alternatives Renewable electricity and hydrogen avoid burning carbon fuels, but have their own costs and limits.

Part 4 of 5Worked Example

Question

  • A power station flue gas contains 6.41 kg of sulfur dioxide.
  • Calculate the mass of calcium carbonate needed to react with it fully, using CaCO₃ + SO₂ → CaSO₃ + CO₂.
  • (Mr: SO₂ 64.1, CaCO₃ 100.1.)

  1. Moles of SO₂ = 6410 g ÷ 64.1 = 100 mol.
  2. The equation shows a 1 : 1 ratio, so 100 mol of CaCO₃ is needed.
  3. Mass of CaCO₃ = 100 × 100.1 = 10 010 g.
  4. Convert to kilograms10 010 g = 10.0 kg to 3 significant figures.

Answer 10.0 kg of CaCO₃

Part 5 of 5Exam Checklist & Tips

3.2.4 – Key Points for the Exam

  • Catalytic converter A device in an exhaust that converts CO, NOₓ and hydrocarbons into less harmful gases.
  • Heterogeneous catalyst A catalyst in a different phase from the reactants, such as a solid catalyst for gases.
  • Flue gas desulfurisation Removing sulfur dioxide from waste gases of power stations.
  • Biofuel A fuel produced from plant or animal material.
  • Carbon neutral Releasing no more CO₂ overall than was taken in.

Common Mistakes

  • Saying that a catalytic converter removes carbon dioxide, when it makes CO₂ from CO and hydrocarbons.
  • Forgetting that catalytic converters work only when hot and can be poisoned.
  • Saying CaO and CaCO₃ remove SO₂ because they are acidic, when they are bases that neutralise the acidic gas.
  • Describing biofuels as having no environmental effect, when growing and processing them still has costs.

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