8 4 A series of experiments was carried out to investigate the factors which affect the rate of reaction between calcium carbonate and dilute hydrochloric acid. CaCO3(s) + 2HCl(aq) → CaCl2(aq) + H2O(l) + CO2(g) • 50.0 cm3 of hydrochloric acid was added to 10 g of calcium carbonate (an excess) in a conical flask placed on an electronic balance. • The loss in mass of the flask and its contents was recorded every 30 seconds for 10 minutes. • The experiment was repeated using different sized pieces of calcium carbonate, a different concentration of hydrochloric acid or a different temperature. Experiment Size of calcium carbonate Concentration of hydrochloric acid / mol dm−3 Temperature /°C 1 small pieces 0.50 20 2 small pieces 0.50 60 3 one large piece 0.50 20 4 small pieces 1.00 20 The results of Experiment 1 are shown on the graph. 1.0 0.8 0.6 0.4 0.2 0 0 120 240 360 480 600 Loss in mass /g Time /s Experiment 1 (a) Draw curves on the graph to show the results you would expect for Experiments 2, 3 and 4. Label the curves 2, 3 and 4. (3) Turn over 9 (b) Determine the initial rate of reaction for Experiment 1. You must show your working on the graph. Include units in your answer. (3) 1.0 0.8 0.6 0.4 0.2 0 0 120 240 360 480 600 Loss in mass /g Time /s Experiment 1 Initial rate of reaction …………………………………………………………………………………………… 10 (c) A student was required to devise an alternative method of carrying out this experiment that involved collecting the gas produced. Outline the procedure that the student could use, including a diagram and the measurements needed. (4) .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... (Total for Question 4 = 10 marks) Turn over 11 BLANK PAGE