AQA Specimen Paper 1 Q9

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24 A 5.00 g sample of potassium chloride was added to 50.0 g of water initially at 20.0 C. The mixture was stirred and as the potassium chloride dissolved, the temperature of the solution decreased. Describe the steps you would take to determine an accurate minimum temperature that is not influenced by heat from the surroundings. [4 marks] . 1 0 9 0 9 . 2 The temperature of the water decreased to 14.6 C. Calculate a value, in kJ mol1, for the enthalpy of solution of potassium chloride. You should assume that only the 50.0 g of water changes in temperature and that the specific heat capacity of water is 4.18 J K1 g1. Give your answer to the appropriate number of significant figures. [4 marks] Barcode Enthalpy of solution = kJ mol1 Typesetter code<br /> . 3 0 9 . 4 0 9 25 The enthalpy of solution of calcium chloride is 82.9 kJ mol1. The enthalpies of hydration for calcium ions and chloride ions are 1650 and 364 kJ mol1, respectively. Use these values to calculate a value for the lattice enthalpy of dissociation of calcium chloride. [2 marks] Lattice enthalpy of dissociation = kJ mol1 Explain why your answer to Question 9.3 is different from the lattice enthalpy of dissociation for magnesium chloride. [2 marks] Barcode Typesetter code Turn over <br />

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