This chemistry question involves key chemical concepts and calculations. The detailed solution below walks through each step, from identifying the reaction type to computing the final answer.
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Here are the solutions: 5. (a) Describe how the cleansing agent removes grease from a piece of cloth. The cleansing agent (detergent) has a hydrophobic (water-hating) hydrocarbon tail and a hydrophilic (water-loving) ionic head (SO_3^-Na^+). The hydrophobic tails dissolve in the grease, while the hydrophilic heads remain in the water. This action lifts the grease from the cloth, forming micelles where the grease is surrounded by the detergent molecules, allowing it to be suspended and washed away by water. 5. (b) Study the flow chart below and answer the questions that follow. (i) State the conditions necessary for fermentation of glucose to take place. Yeast* (as a source of enzymes like zymase) Absence of oxygen* (anaerobic conditions) Temperature of approximately 37^* (ii) State one reagent that can be used to carry out process S. Acidified potassium dichromate(VI)* (K_2Cr_2O_7/H^+) Acidified potassium permanganate(VII)* (KMnO_4/H^+) (iii) Identify gases: I. P: Ethene* (C_2H_4) II. T: Methane* (CH_4) (iv) How is sodium hydroxide kept dry during the reaction (v) Give one commercial use of process R. Sodium hydroxide is kept dry by using it as soda lime*, which is a mixture of sodium hydroxide and calcium oxide (CaO). Calcium oxide acts as a drying agent. Commercial use of process R (hydrogenation of ethene to ethane): Production of saturated hydrocarbons or hardening of vegetable oils* (margarine production). 5. (c) When one mole of ethanol is completely burnt in air, 1370 kJ of heat energy is released. Given that 1 litre of ethanol is 780 g, calculate the amount of heat energy released when 1 litre of ethanol is completely burnt (C=12.0; H=1.0; O=16.0) Step 1: Calculate the molar mass of ethanol (C_2H_5OH). Molar mass of ethanol = (2 × 12.0) + (6 × 1.0) + (1 × 16.0) Molar mass of ethanol = 24.0 + 6.0 + 16.0 = 46.0 g/mol Step 2: Calculate the number of moles in 1 litre of ethanol. Mass of 1 litre of ethanol = 780 g Moles of ethanol = MassMolar mass = 780 g46.0 g/mol Moles of ethanol ≈ 16.9565 mol Step 3: Calculate the total heat energy released. Heat released per mole = 1370 kJ/mol Total heat released = Moles of ethanol × Heat released per mole Total heat released = 16.9565 mol × 1370 kJ/mol Total heat released ≈ 23230.4 kJ The amount of heat energy released is 23230.4 kJ. 5. (d) State two uses of ethanol other than as an alcoholic drink. As a fuel* (e.g., in internal combustion engines) As a solvent* (e.g., in perfumes, cosmetics, and pharmaceuticals) As an antiseptic or disinfectant* As a raw material* in the chemical industry for synthesizing other organic compounds. That's 2 down. 3 left today — send the next one.