Making ethanol by the hydration of ethene

3 marks · Normal

During the hydration of ethene, only 15% of ethene is converted to ethanol in one pass through the reactor. 1000 mol of ethene are used.

Calculate:

(a)

The number of moles of ethene that react.

[1 mark]

(b)

The number of moles of ethene unreacted after one pass.

[1 mark]

(c)

Explain, in one sentence, why the unreacted ethene is recycled in the process.

[1 mark]

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(a) 150 mol

(b) 850 mol

(c) To increase the overall efficiency and ensure more ethene is converted to ethanol. · must show increase yield, use all ethene

Common mistakes: Calculating percentage of product instead of ethene used

Show mark scheme and worked solution

Marking points

M1 (a) · 1 mark · Correct calculation: 15% of 1000 = 150 mol reacts.

M2 (b) · 1 mark · Correct calculation: 1000 – 150 = 850 mol unreacted. (follow-through)

B1 (c) · 1 mark · Clear statement that recycling increases yield or uses all ethene.

Worked solution

(a) Moles that react: 15% of 1000 = 0.15 × 1000 = 150 mol

(b) Moles unreacted: 1000 – 150 = 850 mol