Chemistry-only: steam addition forms an alcohol
| English | Français |
|---|---|
| steam/stiːm/ | vapeur |
| hydration/haɪˈdreɪʃn/ | hydratation |
What would explain this observation?
- Ethene plus steam 水蒸气 can form ethanol. The oxygen atom comes from the water added across C=C; it was not already hidden in the hydrocarbon.
- Start with a prediction. State the quantities or features you would compare, then decide what evidence could distinguish two explanations.
Build the model
- Hydration 水合反应 is addition of water to an alkene. Industrial ethene hydration uses steam at high temperature and pressure with a phosphoric-acid catalyst; about 300 °C and 60 atmospheres are representative conditions. One H₂O supplies H to one formerly double-bonded carbon and OH to the other, while C=C becomes single. Ethene forms ethanol: C₂H₄ + H₂O → C₂H₅OH. The carbon skeleton is retained.
- hydration: Addition of water across a multiple bond in the stated alkene reaction; steam: Water in the gaseous state.
Which combination describes the taught industrial ethene hydration?
The product is an alcohol, not a hydrocarbon, because it now contains oxygen. Count the H inside OH as well as those bonded directly to carbon. Ethene’s two carbons are equivalent in this simple addition. Unsymmetrical starting alkenes can give different OH positions: the longer terminal-chain panels show the usual secondary-alcohol arrangement with OH on the second carbon. These drawings identify stated products without adding a required advanced mechanism or demanding positional product names beyond the course scope.
Match each technical term to its precise meaning.
Use the definitions to distinguish related quantities and processes.
Choose evidence that can test it
- The product is an alcohol, not a hydrocarbon, because it now contains oxygen. Count the H inside OH as well as those bonded directly to carbon. Ethene’s two carbons are equivalent in this simple addition. Unsymmetrical starting alkenes can give different OH positions: the longer terminal-chain panels show the usual secondary-alcohol arrangement with OH on the second carbon. These drawings identify stated products without adding a required advanced mechanism or demanding positional product names beyond the course scope.
- Draw all bonds including C–O and O–H, and check carbon four, oxygen two and hydrogen one. Compare the product with the input molecule and steam rather than adding OH alone and losing the extra H. The paired first-four displays show before/after connectivity. These industrial conditions are reference information, not a school pressurised synthesis task. Actual school work can use models and supplied process evidence under supervision.
Which two habits make the investigation or model in this case more defensible?
Draw all bonds including C–O and O–H, and check carbon four, oxygen two and hydrogen one. Compare the product with the input molecule and steam rather than adding OH alone and losing the extra H. The paired first-four displays show before/after connectivity. These industrial conditions are reference information, not a school pressurised synthesis task. Actual school work can use models and supplied process evidence under supervision.
Work from known quantities
- State the known values and their units. Choose the relation because its assumptions fit this case, then rearrange before substitution.
- Known: ethene has four hydrogen atoms. Adding water contributes two, so ethanol contains six H in total: five attached to carbon and one to oxygen. Its total atom count is 2 C + 6 H + 1 O = 9. A displayed product from C₃H₆ plus water has C₃H₈O, eleven atoms in total. The formula alone does not specify the OH position.
The product of adding one water molecule to C₄H₈ is C₄H₁₀O. Find its total atom count. Use the same sequence: known quantities → model → relation → substitution → unit and interpretation.
The product of adding one water molecule to C₄H₈ is C₄H₁₀O. Find its total atom count.
The result is 15 atoms. Known: ethene has four hydrogen atoms. Adding water contributes two, so ethanol contains six H in total: five attached to carbon and one to oxygen. Its total atom count is 2 C + 6 H + 1 O = 9. A displayed product from C₃H₆ plus water has C₃H₈O, eleven atoms in total. The formula alone does not specify the OH position.
Check the conclusion and its limits
- Do not use cold liquid water alone as the specified ethene hydration condition or substitute nickel for phosphoric acid. Hydrogen addition gives an alkane; steam addition gives an alcohol. Industrial reaction need not convert every molecule in one pass. Hydration is distinct from the yeast fermentation route to an aqueous ethanol solution.
- Return to the original observation. Explain what the result supports, which conditions it assumes, and one way to test a competing explanation.
Steam addition to ethene produces an alkane containing no oxygen. This claim is false: Do not use cold liquid water alone as the specified ethene hydration condition or substitute nickel for phosphoric acid. Hydrogen addition gives an alkane; steam addition gives an alcohol. Industrial reaction need not convert every molecule in one pass. Hydration is distinct from the yeast fermentation route to an aqueous ethanol solution.
Chemistry-only: steam addition forms an alcohol: The product is an alcohol, not a hydrocarbon, because it now contains oxygen. Count the H inside OH as well as those bonded directly to carbon. Ethene’s two carbons are equivalent in this simple addition. Unsymmetrical starting alkenes can give different OH positions: the longer terminal-chain panels show the usual secondary-alcohol arrangement with OH on the second carbon. These drawings identify stated products without adding a required advanced mechanism or demanding positional product names beyond the course scope.
Steam addition to ethene produces an alkane containing no oxygen.
Do not use cold liquid water alone as the specified ethene hydration condition or substitute nickel for phosphoric acid. Hydrogen addition gives an alkane; steam addition gives an alcohol. Industrial reaction need not convert every molecule in one pass. Hydration is distinct from the yeast fermentation route to an aqueous ethanol solution.
Addition of water across a multiple bond in the stated alkene reaction: write the technical term.
hydration means Addition of water across a multiple bond in the stated alkene reaction.