Edexcel Jan 2012 Paper 4 Q20 (with explained solutions) |

Skip to content

Edexcel Jan 2012 Paper 4 Q20

Answers available below

PMT 20 The exothermic reaction between carbon monoxide and hydrogen can be used industrially to make methanol. The process is carried out at 250 (cid:113)C and between 50 and 100 atm. CO(g) + 2H2(g) (cid:85) CH3OH(g) (a) Explain why increasing the pressure increases the yield of methanol. Give one disadvantage of increasing the pressure. (2)(b) The reaction gives a greater equilibrium yield at 100 (cid:113)C than at 250 (cid:113)C. (i) Explain, in terms of the entropy change of the surroundings and the total entropy change of the reaction, why this is so. A calculation is not required. (2)(ii) Explain why the reaction is, nevertheless, carried out at 250 (cid:113)C. (1)(c) Given that the reaction is an equilibrium, suggest two ways in which the atom economy of this process could be maximised without changing the temperature or pressure. (2)(Total for Question 20 = 7 marks) 14 *P39304A01424*<br />

Show answer

Question Number 20(a) Acceptable Answers Reject Mark (Greater yield) as fewer moles/molecules (of gas) on RHS OR 3 moles/molecules on left but only 1 on right (1) ALLOW arguments in terms of Kp remaining constant Disadvantage: Extra cost of Just (higher) (building) equipment (to withstand higher pressure)/ cost thicker pipes/compressor/maintaining equipment (1) OR Higher cost of energy needed for compression (1) IGNORE references to explosion Question Number 20(b)(i) (Reaction is exothermic) so the value of D Ssurroundings Acceptable Answers Reject Mark becomes more positive/larger (at 100 C) (1) Therefore D Stotal becomes more positive/larger/less negative(at 100 C) (1) Second mark consequential on first Question Number 20(b)(ii) (Higher temperature gives a) faster rate of reaction Acceptable Answers Reject /more particles have EEa (ALLOW more successful collisions (per second) IGNORE references to yield Question Number 20(c) Acceptable Answers Reject Remove methanol/the product (as it is formed) (1) Recycle/reuse unreacted reactants (1) IGNORE references to catalyst and increasing amounts of reactants Mark Mark 6CH0401 1201<br />

Question 17 18 19 20 21 22 23

About us | Need Help? | Feedback

Proudly powered by WordPress | Theme: Sydney by aThemes.