ما هي معادلة الأسترة وكيف يتكون الإستر؟ What is the esterification reaction equation?

تفاعل الأسترة هو تفاعل انعكاسي بين حمض كربوكسيلي وكحول في وجود حمض الكبريتيك المركز كعامل حفاز لنزع الماء: R-COOH + R2-OH ⇌ R-COO-R2 + H₂O، ونواتجه إستر وماء. [الصيغة الرمزية الموزونة: R-COOH + R2-OH ⇌ (conc. H₂SO₄) R-COO-R2 + H₂O]

4bOrganic Chemistry

Crude oil — Edexcel Linear - OL (Chemistry) Revision Notes & Topical Questions

10 min read 13 parts Lesson 2 of 18 1 quiz

📚 Edexcel Linear - OL (Chemistry) Hub / Topical Revision

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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Lesson summary

Crude oil Edexcel O Level Linear Chemistry notes: know that crude oil is a mixture of hydrocarbonsCracking meets demand for smaller fuels and makes alkenes.Plastics cause pollution because they are non-biodegradable.Recycling and biodegradable polymers reduce waste.know that crud…

Crude oil Edexcel O Level Linear Chemistry: what to do next
Fractional distillation
Addition polymer
Condensation polymer
Give / State / Name
Evaluate / Assess

Section 1 of 13Process & sequence

Crude oil heated

Vapour rises up column

Cooler at top

Fractions condense at different heights

Polymers

Poly(ethene) – bags

Poly(propene) – crates

PVC – pipes

Nylon – clothing (condensation)

Section 2 of 13Keep going

Crude oil Edexcel O Level Linear Chemistry: what to do next

These Crude oil Edexcel O Level Linear Chemistry notes covered the key ideas, worked examples and exam technique for this topic. Check your Crude oil Edexcel O Level Linear Chemistry understanding with the practice questions below, then reread any Crude oil Edexcel O Level Linear Chemistry point you were unsure about before moving on.

Practice: Crude oil Edexcel O Level Linear Chemistry practice questions

Previous lesson: 4a Introduction — Notes

Next lesson: 4c Alkanes — Notes

Course: Edexcel Linear – OL (chemistry) — all units

Official syllabus: Pearson Edexcel International GCSEs

Section 3 of 13Supply, demand and cracking

The fractional distillation of crude oil gives more of the long-chain fractions (fuel oil, bitumen) than the market needs, while the demand for shorter chains (petrol, naphtha, alkenes) is greater. Cracking converts long-chain alkanes into shorter, more useful molecules. It is a thermal decomposition reaction, not a reaction with oxygen.

Type	Conditions	Main products
Catalytic cracking	About 500 °C, zeolite catalyst	Petrol-range alkanes and alkenes
Steam cracking	About 850 °C, steam, no catalyst	Ethene, propene

Example

C₂₀H₄₂ → C₁₀H₂₂ + 2C₅H₁₀ (carbons 10 + 10 = 20;
- hydrogens 22 + 20 = 42).
The alkene products are used for polymers and as chemical feedstocks.

Section 4 of 13Combustion products and their effects

Pollutant	Source	Effect
Carbon dioxide	Complete combustion	Greenhouse effect, global warming
Carbon monoxide	Incomplete combustion	Toxic gas
Carbon (soot)	Incomplete combustion	Global dimming, breathing problems
Sulfur dioxide	Sulfur impurities in fuel	Acid rain
Nitrogen oxides	Nitrogen and oxygen at engine temperature	Acid rain, smog, respiratory disease

Acid rain damages trees, aquatic life and limestone buildings. It can be reduced by removing sulfur from fuels before burning, flue gas desulfurisation with calcium oxide or calcium carbonate (SO₂ + CaO → CaSO₃), and catalytic converters, which convert CO and NO_x to CO₂ and N₂.

Section 5 of 13Alternatives and conservation

Crude oil is finite, so strategies include improving efficiency, public transport, biofuels (ethanol, biodiesel), hydrogen fuel cells and electric vehicles powered by renewable electricity. Oil is also needed for plastics, medicines and solvents, so burning it all as fuel is wasteful. Oil spills are cleaned using dispersants, booms and skimmers, but the damage to marine life can last for years.

Section 6 of 13Compare

Crude oil fractions
Fraction	Carbon atoms	Boiling point	Viscosity	Flammability	Use
Refinery gas	1–4	Lowest	Lowest	Highest	Bottled gas
Petrol (gasoline)	5–10	Low	Low	High	Car fuel
Naphtha	8–12	—	—	—	Chemicals, cracking
Kerosene	10–16	Medium	Medium	Medium	Jet fuel
Diesel	14–20	Higher	Higher	Lower	Lorries, trains
Fuel oil	20–40	High	High	Low	Ships, power stations
Bitumen	> 50	Highest	Highest	Lowest	Roads, roofing

Section 7 of 13Worked questions and calculations

Pollutant calculationburning 1 mol (114 g) of octane in an engine produces 8 mol of CO₂ (352 g) by the equation 2C₈H₁₈ + 25O₂ → 16CO₂ + 18H₂O, so the mass of carbon dioxide released is about 3.1 times the mass of fuel.

Worked questions and calculations

Burning 10 kg of petrol therefore gives roughly 31 kg of carbon dioxide, showing why transport is a major source of greenhouse gases.

Sulfur dioxide example: coal containing 1% sulfur burning at 1000 tonnes per day releases about 20 tonnes of SO₂ per day (10 tonnes of sulfur, doubled by oxygen),

unless scrubbers are used.

Evaluate fuel choices in a tablecoal (cheap, abundant, high CO₂ and SO₂), natural gas (less CO₂ per unit energy, no soot), nuclear (no CO₂ but waste), hydrogen (no CO₂, storage issues), biofuel (renewable, land use).

Worked questions and calculations

Credit is given for balanced judgement and a justified conclusion.

Link also to the tests you can perform: carbon dioxide turns limewater milky, water is shown by cobalt chloride paper turning pink,

and sulfur dioxide decolourises acidified potassium manganate(VII) from purple to colourless,
which is used to detect it.

Section 8 of 13Revision checklist for crude oil questions

Be able to

(1) state that crude oil is a mixture of hydrocarbons separated by fractional distillation based on boiling point;
- (2) list the fractions in order with a use for each;
- (3) describe how boiling point, viscosity and flammability change with chain length and explain this by intermolecular forces;
- (4) write and balance cracking equations and name the conditions;
- (5) describe the pollutants made when fuels burn and the matching control measures;
- (6) evaluate fuels using energy released, cost, sustainability and pollution.
A typical six-mark answer on fractional distillation follows the sequence heated, vapour rises, temperature gradient, condensation at the boiling point, drawn off, using the words "lower boiling points are collected nearer the top".

Section 9 of 13Worked examples

Explain why cracking is carried out. [2]2 marks
Balance C₁₈H₃₈ → C₈H₁₈ + 2C₅H₁₀: show carbon and hydrogen counts. [2]2 marks
How does a catalytic converter reduce pollution? [2]2 marks
Why does burning fuels cause acid rain? [2]2 marks

Section 10 of 13Key terms

Term	Meaning
Catalytic cracking	Cracking with a catalyst at high temperature
Steam cracking	Cracking with steam at very high temperature
Flue gas desulfurisation	Removal of SO₂ from power station gases
Acid rain	Rain made acidic by SO₂ and NOx
Biofuel	Fuel from plant material
Feedstock	Raw material for chemical industry

Section 11 of 13Syllabus checklist

know that crude oil is a mixture of hydrocarbons

describe how the industrial process of fractional distillation separates crude oil into fractions

know the names and uses of the main fractions obtained from crude oil

refinery gases
gasoline
kerosene, diesel
fuel oil and bitumen

know the trend in colour, boiling point and viscosity of the main fractions

know that a fuel is a substance that, when burned, releases heat energy

know the possible products of complete and incomplete combustion of hydrocarbons with oxygen in the air

understand why carbon monoxide is poisonous, in terms of its effect on the capacity of blood to transport oxygen references to haemoglobin are not required

know that, in car engines, the temperature reached is high enough to allow nitrogen and oxygen from air to react, forming oxides of nitrogen

explain how the combustion of some impurities in hydrocarbon fuels results in the formation of sulfur dioxide

understand how sulfur dioxide and oxides of nitrogen contribute to acid rain describe how long-chain alkanes are converted to alkenes and shorter-chain alkanes by catalytic cracking (using silica or alumina as the catalyst and a temperature in the range of 600-700-C)

explain why cracking is necessary, in terms of the balance between supply and demand for different fractions

Section 12 of 13Command terms

Command terms

Give / State / Name

Recall a fact; one idea per mark.

Define

Give the exact meaning using the specification keywords.

Describe

Give an account of what happens / the pattern in data, quoting values; no reasons needed.

Explain

Give reasons with linked statements (cause → effect). Each linked step is usually a separate marking point.

Suggest

Use knowledge in a new context; more than one answer may be accepted.

Compare

Similarities and differences; each point must refer to both items.

Calculate

Show working; include units; check significant figures. Method marks are given even if the final answer is wrong.

Discuss

Explore the issue from different angles and link the points.

Evaluate / Assess

Weigh strengths and weaknesses and reach a supported judgement.

Deduce

Draw a conclusion from the information given.

Justify

Support a statement/choice with evidence.

Section 13 of 13Exam technique

Saying cracking uses oxygen.

Saying cracking makes only alkanes.

Confusing global warming with acid rain.

Blaming CO₂ for acid rain.

Last updated: 11 October 2026