Ethene is produced from ethanol by

Analyze the question: It asks which process converts ethanol (C₂H₅OH) into ethene (C₂H₄).

Concept: When ethanol is heated with excess concentrated sulphuric acid at about 170 °C (or passed over hot alumina, Al₂O₃), a water molecule is removed from each ethanol molecule. Removing water from a compound is called dehydration. It is an elimination reaction that forms a double bond.

Solution:

C₂H₅OH → C₂H₄ + H₂O (conc. H₂SO₄, 170 °C)

• The –OH group is removed from one carbon.
• An –H is removed from the neighbouring carbon.
• Together they leave as H₂O, and a C=C double bond forms.

Checking the options:

• A. Decomposition: This is too general. It means breaking a compound into simpler substances, and it does not name the specific process of removing water.
• B. Hydrolysis: This is the reaction of a compound with water to break it down. It is the opposite of what happens here, because water is removed, not added.
• C. Ozonolysis: This is the cleavage of C=C bonds by ozone. It does not apply here.
• D. Dehydration: Correct, because water is removed from ethanol.

**Answer: D. Dehydration.

Exam tip: Remember "Ethanol → Ethene = Dehydration (lose water)." The reverse reaction, ethene + steam → ethanol, is hydration. In WASSCE, a conc. H₂SO₄ catalyst with heat usually signals a dehydration question.