9701 MCQ Solution 69

Question 69: [Organic > Hydroxyl Compounds]

In a preparation of ethene, ethanol is added a drop at a time to a heated reagent Y. To purify the ethane it is bubbled through a solution Z and then collected.

What could reagent reagent Y and solution Z be?

	reagent Y	solution Z
A	acidified K2Cr2O7	dilute NaOH
B	concentrated H2SO4	dilute H2SO4
C	concentrated H2SO4	dilute NaOH
D	ethanolic NaOH	concentrated H2SO4

Reference: Past Exam Paper –June 2003 Paper 1 Q29

Solution 69:

Answer: C.

Alcohol undergoes dehydration to form an alkene. Concentrated H₂SO₄ is among the possible conditions for this reaction. This eliminates options A and D as possible answers. After dehydration occurs there may be remaining H₂SO₄ mixed with the alkene. This remainder must be neutralised. It is acidic and in option B, the addition of more H₂SO₄ will contaminate the alkene more, thus is an incorrect answer. A basic solution will neutralise the acid, such as the dilute NaOH in option C, which is the correct answer.