Making ethanol by the hydration of ethene
4 marks · NormalList the three main conditions (temperature, pressure, and catalyst) used for the industrial hydration of ethene to make ethanol.
State why a phosphoric acid catalyst is used in this process.
Explain why the pressure used is not even higher than 70 atmospheres, even though increasing pressure can raise yield.
Work this out on paper, then compare with the answer and worked solution below. With a free account you can submit written answers for marking.
Show answer
(a) 300°C, 60–70 atmospheres, phosphoric acid (H3PO4)
(b) It speeds up the reaction or increases the rate.
(c) Because higher pressures increase costs and create safety concerns; equipment must be stronger and more expensive, so a compromise is chosen. · must show cost, equipment, compromise
Show mark scheme and worked solution
Marking points
B1 (a) · 2 marks · Lists any two correct conditions for full marks; one correct condition for one mark (temp 300°C, pressure 60–70 atm, catalyst phosphoric acid/H3PO4).
B2 (b) · 1 mark · States that catalyst speeds up reaction/increases rate.
B3 (c) · 1 mark · Explains higher pressure is not used because of cost, equipment limits, or safety (must refer to practical/financial reason).
Worked solution
(a) The three main conditions: 300°C, 60–70 atmospheres, phosphoric acid catalyst.
(b) Phosphoric acid is used as a catalyst to speed up the reaction.
(c) Very high pressures are expensive and require special equipment; a compromise is made for reasonable yield and cost.