Ethanol from ethene: steam, pressure and acid catalyst
Describe catalytic hydration with the exact required temperature and pressure, retaining steam's oxygen in the ethanol product.
Section C12.6 · Alcohols
Cross-referenced from the related Cambridge IGCSE Chemistry 0620 or Physics 0625 teaching to the 0652 syllabus. Exact 0652 Core/Supplement objective coverage and this final-series course’s examiner fit still need specialist review. Written practice is self-checked and does not predict a Cambridge grade or demonstrate supervised laboratory competence.
Before you begin
- Read ethene's C=C and ethanol's C–O–H connections.
- Distinguish steam addition from hydrogen addition.
Work on paper. Try each question before revealing help, and explain why your method works.
Quick readiness check
Which reagent supplies ethanol's oxygen in this route?
What you will learn
- State 300°C, 6000 kPa / 60 atm and an acid catalyst for ethene hydration.
- Explain how ethene and steam form ethanol in the stated addition reaction.
Match the complete industrial condition set
The required catalytic addition of steam to ethene uses 300°C and 6000 kPa / 60 atm, with an acid catalyst. State ethene plus steam, not glucose plus yeast. The syllabus gives the pressure as 6000 kPa / 60 atm; use those stated exam values rather than introducing a false claim that an exact metrological atmosphere is defined as precisely 100 kPa.
The reaction is hydration: C₂H₄+H₂O→C₂H₅OH, also written CH₂=CH₂+H₂O→CH₃CH₂OH. The C=C becomes C–C, with H and OH added across it. One ethanol molecule contains all the atoms of the stated ethene and water reactants. The acid catalyst is a reaction condition, not an extra atom source in ethanol's molecular formula.
Keep manufacture routes and reagents separate
Steam provides both oxygen and hydrogen. Hydrogen with nickel instead converts ethene to ethane, so those reagents cannot substitute for steam and an acid catalyst when ethanol is the required product. Glucose fermentation uses yeast, a lower temperature and no oxygen; it is not described by this ethene equation.
The displayed ethanol structure introduced earlier shows three H on the first carbon, two on the next carbon and one in O–H. Its molecular total is C₂H₆O, even when written C₂H₅OH. The equation describes the required reaction and conditions; it does not establish 100% conversion per pass, product purity or the economics of a particular plant.
Sources for this lesson
Pause and explain
Which pairing manufactures ethanol by the required hydration route?
Worked example
Give ethene hydration's reactants, product and required temperature, pressure and catalyst.
Show the worked solution
- Ethene reacts with steam: C₂H₄+H₂O→C₂H₅OH.
- The required conditions are 300°C and 6000 kPa / 60 atm with an acid catalyst.
- The product is ethanol, total C₂H₆O, with the oxygen retained in its OH group.
Answer Ethene + steam → ethanol; C₂H₄+H₂O→C₂H₅OH at 300°C, 6000 kPa / 60 atm, with an acid catalyst.
Try a topic test
Choose Easy, Normal or Difficult. Save your answers and open worked review after finishing.
Test this topic →From guided practice to a new situation
Write your answer and reasoning first. Use a hint only if you are stuck. The model solution is for self-checking; your written work is not automatically marked.
Write the hydration equation and label every specified condition.
Give me a hint
Give both reactants before listing temperature, pressure and catalyst.
Compare my reasoning
- C₂H₄+H₂O→C₂H₅OH uses ethene and steam to form ethanol.
- State 300°C and 6000 kPa / 60 atm.
- State an acid catalyst, without placing catalyst atoms in the product formula.
C₂H₄+H₂O→C₂H₅OH; 300°C, 6000 kPa / 60 atm, acid catalyst.
Look for these in your work
- The product and atom sources are correct.
- All required conditions are included.
Compare the molecular totals in C₂H₄+H₂O→C₂H₅OH and explain how the product structure changes.
Give me a hint
Include the H within OH and change the carbon bond order.
Compare my reasoning
- Reactants total C₂H₆O.
- C₂H₅OH also totals C₂H₆O, including the O–H hydrogen.
- C=C becomes C–C with H and OH added, giving CH₃CH₂OH.
C₂H₆O on both sides; C=C becomes C–C and H/OH addition gives CH₃CH₂OH.
Look for these in your work
- Atom totals include the OH hydrogen.
- The connectivity change matches ethanol.
An answer lists ethene plus hydrogen, nickel and 25°C but predicts ethanol. Correct it for the specified industrial ethanol route and state the separate hydrogenation product.
Give me a hint
The ethanol route needs an oxygen-containing reagent.
Compare my reasoning
- Use ethene and steam rather than hydrogen alone.
- State 300°C, 6000 kPa / 60 atm and an acid catalyst for the required hydration.
- Ethene plus hydrogen with nickel instead gives ethane, C₂H₆.
Ethanol: ethene + steam, 300°C, 6000 kPa / 60 atm, acid catalyst. Hydrogen/Ni instead gives ethane C₂H₆.
Look for these in your work
- All incorrect route features are corrected.
- The alternative reagent's product is distinguished.
Common mistakes
- Omitting pressure or replacing it with the fermentation conditions.
- Using nickel and hydrogen while still predicting ethanol.
- Counting C₂H₅OH as only five hydrogens.
- Treating the stated pressure equivalence as an exact definition of the atmosphere unit.
What can you explain now?
Give the required temperature, pressure and catalyst for ethene hydration.
Compare with the explanation
300°C, 6000 kPa / 60 atm and an acid catalyst.
These are the specified syllabus conditions for catalytic addition of steam to ethene.
After trying it yourself, choose your next review. This is your self-assessment.
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Make it stick
Recall the full hydration condition set, balance its equation and explain why nickel/hydrogen cannot supply ethanol's oxygen.
If you needed the solution, close it and solve the problem again from a blank page. A correct answer is stronger when you can explain the reason for each step.