ALS7Q - Section 7/ Phase Equilibrium / 1 SKH Bishop Baker...

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Section 7/ Phase Equilibrium / SKH Bishop Baker Secondary School AL Chemistry Section 7 Phase Equilibrium 80 IA Q.2 (a) (iii) A mixture of three amino acids A , B and C was separated by 2-way paper chromatography, i.e. carrying out the chromatography first in one direction and then in a direction at right angle to the first. The R f values of these three amino acids are given below : Amino acid R f value in phenol R f value in butan-1-ol/ethanoic acid A B C 0.30 0.45 0.65 0.25 0.40 0.70 where solvent by travelled distance acid amino by travelled distance value R f = On the diagram below, mark (using crosses) and label the positions A , B and C . (2 marks) 80 IB Q.9 (a) A boiling point - composition graph for mixtures of water and hydrochloric acid as obtained experimentally as shown. 1
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Section 7/ Phase Equilibrium / (i) If the distillate at 108.0 o C had been collected and put into another distillation flask and distilled, what would be the boiling point and concentration of HCl (in mol dm -3 ) of its vapour ? (2 marks) (ii) 50 cm 3 of 4.5 M hydrochloric acid was distilled until the residue had a volume of about 2 cm 3 . Discuss what happened during the course of distillation. (4 marks) (iii) Suggest one use for the distillate collected at 108.6 o C. (2 marks) (b) (i) Describe how a fractionating column works to separate mixtures into their component parts in distillation. (4 marks) (ii) Give two industrial applications of fractional distillation. (2 marks) 81 IB Q.9 (b) Ammonia reacts with a metal ion M 2+ in aqueous solution to from a soluble complex [M(NH 3 ) x ] 2+ . The experiment below was carried out in order to determine the formula of the complex ion. Excess aqueous ammonia was added to 25.00 cm 3 of a 0.10 M aqueous solution of M 2+ . The total volume of the resulting solution was 50.00 cm 3 . This solution was shaken with trichloromethane and allowed to settle. The concentration of ammonia in the trichloromethane layer was found by titration, in which 25.00 cm 3 of the layer required 12.70 cm 3 of 0.05 M hydrochloric acid for neutralization. The total concentration of ammonia (free and complexed) in the aqueous layer was found by titration, in which 25.00 cm 3 required 41.60 cm 3 of 0.50 M hydrochloric acid for neutralization. Assume that the partition coefficient of ammonia between water and trichloromethane at the temperature of the experiment is 25, and that the complex remains in the aqueous layer. (i) How would you withdraw the 25.00 cm 3 of the trichloromethane layer required for titration ? (2 marks) 2
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Section 7/ Phase Equilibrium / (ii) During the titration of the aqueous layer, what equilibrium change takes place ? (1 mark) (iii) How many molecules of ammonia are coordinated with each M 2+ ion ? Show your calculation. (5 marks)
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This note was uploaded on 08/17/2011 for the course CHEM 100 taught by Professor Fleet during the Fall '08 term at Oxford University.

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ALS7Q - Section 7/ Phase Equilibrium / 1 SKH Bishop Baker...

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