a. i. Using a schematic diagram, show the main components of a double beam UV-visible spectrophotometer. (4 marks) ii. Differentiate between bathochromic and hypsochromic shifts in UV-visible spectroscopy. (2 marks) iii. A UV-visible spectrophotometric analysis of a solution shows an absorbance of 0.52 at 520 nm. What percentage of radiation is transmitted? (2 marks) iv. A compound with a molar absorptivity of 3578 dm mol cm exhibits an absorbance of 0.78 when placed in a 1 cm path length cuvette in a UV-visible spectrophotometer. Calculate the concentration of the compound. (2 marks) b. Phosphorescent spectrocopy can be viewed as a competitive or complementary technique to fluorescence spectroscopy i. Explain how molecular phosphorescence occurs (3 marks) ii. State two factors that could favour molecular phosphorescence over fluorescence. (2 marks) c. Supercritical fluids are increasingly used as extraction solvents and as mobile phases in chromatography i. What is a supercritical fluid? ii. Give one example of a supercritical fluid? (1 mark) (1 mark) iii. State three advantages of using supercritical fluids. (3 marks)