AQA Jun 2017 Paper 2 Q8

Answers available below

150 8 0 8 . 1 This question is about nitrobenzenes. Nitrobenzene reacts when heated with a mixture of concentrated nitric acid and concentrated sulfuric acid to form a mixture of three isomeric dinitrobenzenes. Write an equation for the reaction of concentrated nitric acid with concentrated sulfuric acid to form the species that reacts with nitrobenzene. [1 mark] 0 8 . 2 Name and outline a mechanism for the reaction of this species with nitrobenzene to form 1,3-dinitrobenzene. Name of mechanism Mechanism [4 marks] Turn over for the next question *15* Turn overIB/M/Jun17/7405/2<br /> 16The dinitrobenzenes shown were investigated by thin layer chromatography (TLC). In an experiment, carried out in a fume cupboard, a concentrated solution of pure 1,4-dinitrobenzene was spotted on a TLC plate coated with a solid that contains polar bonds. Hexane was used as the solvent in a beaker with a lid. The start line, drawn in pencil, the final position of the spot and the final solvent front are shown on the chromatogram in Figure 3 0 8 . 3 *16* Figure 3 Use the chromatogram in Figure 3 to deduce the Rf value of 1,4-dinitrobenzene in this experiment. Tick () one box. A 0.41 B 0.46 C 0.52 D 0.62 [1 mark] IB/M/Jun17/7405/2<br /> 0 8 . 4 0 8 . 5 0 8 . 6 17State in general terms what determines the distance travelled by a spot in TLC. [1 mark] To obtain the chromatogram, the TLC plate was held by the edges and placed in the solvent in the beaker in the fume cupboard. The lid was then replaced on the beaker. Give one other practical requirement when placing the plate in the beaker. [1 mark] A second TLC experiment was carried out using 1,2-dinitrobenzene and 1,4-dinitrobenzene. An identical plate to that in Question 8.3 was used under the same conditions with the same solvent. In this experiment, the Rf value of 1,4-dinitrobenzene was found to be greater than that of 1,2-dinitrobenzene. Deduce the relative polarities of the 1,2-dinitrobenzene and 1,4-dinitrobenzene and explain why 1,4-dinitrobenzene has the greater Rf value. [2 marks] Relative polarities Explanation *17* Turn overIB/M/Jun17/7405/2<br /> 18A third TLC experiment was carried out using 1,2-dinitrobenzene. An identical plate to that in Question 8.3 was used under the same conditions, but the solvent used contained a mixture of hexane and ethyl ethanoate. A student stated that the Rf value of 1,2-dinitrobenzene in this third experiment would be greater than that of 1,2-dinitrobenzene in the experiment in Question 8.6 Is the student correct? Justify your answer. [2 marks] 0 8 . 7 12 *18* IB/M/Jun17/7405/2<br />

Show answer