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# 9_phase - < phase/AL91P2_3b 3(b(i A liquid is added as a...

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<<< phase/AL91P2_3b 3. (b) (i) A liquid is added as a solvent forming an ideal solution. Comment on the vapour pressure of the solution as compared with that of the pure solvent. (ii) The vapour pressures of pure methanol and ethanol at 25 o C are 89.2 mm Hg and 44.6 mm Hg respectively. A mixture containing 32.0 g of methanol and 184.0 g of ethanol behaves as an ideal solution. Calculate the partial vapour pressure of each component, the total vapour pressure of the mixture and the composition of the vapour. (Relative atomic masses : H, 1.9; C, 12.0; O, 16.0) (7 marks) <<< phase/AL92P1_2f 2. (f) The vapour pressure versus mole fraction diagram for a two component system (A and B) is shown below: (i) State the reason(s) which give(s) rise to the shapes of the curves in the diagram. (ii) What do points P and Q represent? (iii) What assumption(s) would have to be met for the curves to be linear? Give an equation to represent this behaviour. (4 marks) <<< phase/AL92P1_2g 2. (g) For the phase diagram below: (i) Identify the points X and Y. (ii) Which two points in the diagram define the sublimation curve? (iii) Mark on the diagram, using the symbol B, the normal boiling point. (iv) Suggest the meaning of the curve YW. (4 marks) ALP_topics/phase eq/p.1(6)

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<<< phase/AL92P2_2c 2. (c) (i) The distribution coefficient of a compound X between two immiscible liquids D and E is 12. X is more soluble in D. What mass of X can be attracted from 50 cm 3 of a solution of E which initially contains 4 g of X when shaken with 100 cm 3 of D? (ii) The total vapour pressure exhibited by a mixture of immiscible liquids is equal to the sum of their individual saturated vapour pressures. (I) Explain why steam distillation enables some heat-sensitive organic compounds to be distilled at a lower temperature than their normal boiling points. (II) A mixture of two immiscible liquids F and G boils at 98 o C. At this temperature, the vapour pressure of F and G are 733 mmHg and 27 mmHg respectively, Calculate the percentage of G by mass in the vapour when the mixture boils. (The relative molecular masses of F and G are 18.0 and 123.0 respectively.) (7 marks) <<< phase/ AL93P2_1a 1. (a) Liquid A is miscible with liquid B over the whole composition range, forming ideal solutions. The vapour pressures of pure A and pure B, measured at 350 K, are 24.0 kPa and 12.0 kPa respectively. (i) Calculate the vapour pressure of a liquid mixture consisting of 60 mole % A and 40 mole % B at 350 K.
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