page 11 23. Salbutamol is used to treat asthma. It behaves like the body’s natural active compound by triggering a response in the muscles of the airways. Salbutamol is A an agonist B an antagonist C an inhibitor D a receptor. 24. 200 cm3 of water is added to 50 cm3 of 2 mol l-1 sodium hydroxide solution. The concentration of the diluted sodium hydroxide solution in mol l-1, is A 0·5 B 0·4 C 0·2 D 0·1. 25. For solvent extraction from an aqueous solution, the solvent used should be immiscible with water and relatively unreactive. Which of the following would be the most suitable solvent? A CH3CH2CH2CH2CHO B CH3CH2OCH2CH2CH3 C CH3CH2CH2CH2COOH D CH3CH(OH)CH2CH2CH3 26. Which of the following is not a step in a recrystallisation technique? A Allow the filtrate to cool slowly. B Filter the hot solution to remove insoluble impurities. C Dissolve the crystals in a minimum of hot solvent. D Test the filtrate to ensure no more precipitate forms. [Turn over