page 13 25. The progress of a reaction was followed by periodically sampling the reaction mixture and analysing it using thin‑layer chromatography. The chromatogram for the analysis of one sample is shown. R is a spot of pure reactant C is a co‑spot of pure reactant and the reaction mixture sample S is a spot of the reaction mixture sample R C S Which of the following conclusions must be correct for this thin‑layer chromatogram? A The reaction mixture does not contain impurities. B All of the reactant has been used up. C Only the desired product is present. D The reaction is complete. [END OF SECTION 1. NOW ATTEMPT THE QUESTIONS IN SECTION 2 OF YOUR QUESTION AND ANSWER BOOKLET.] page 14 [BLANK PAGE] DO NOT WRITE ON THIS PAGE page 15 [BLANK PAGE] DO NOT WRITE ON THIS PAGE page 16 [BLANK PAGE] DO NOT WRITE ON THIS PAGE