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F5 Chem calculation
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In an experiment, 10 g of KCl(s) was added to 100 cm^3 of water. The mixture was then stirred until all the KCl(s) dissolved. The temperature of the mixture was found to drop by 5.5 degree Celsius. What is the molar enthalpy change, in kJ mol^-1, of the dissolving process of KCl(s) under the conditions of the... 顯示更多 In an experiment, 10 g of KCl(s) was added to 100 cm^3 of water. The mixture was then stirred until all the KCl(s) dissolved. The temperature of the mixture was found to drop by 5.5 degree Celsius. What is the molar enthalpy change, in kJ mol^-1, of the dissolving process of KCl(s) under the conditions of the experiment? ( Specific heat capacity of the mixture = 4.2Kg^-1K^-1; Density of water =1.0 g cm^-3; Relative atomic masses: K = 39.1, Cl = 35.5) Ans: 18.96. Show me the steps please.
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In an experiment, 10 g of KCl(s) was added to 100 cm3 of water. The mixture was thenstirred until all the KCl(s) dissolved. The temperature of the mixture was foundto drop by 5.5 degree Celsius. What is the molar enthalpy change, in kJmol?1, of the dissolving processof KCl(s) under the conditions of the experiment? ( Specific heat capacity ofthe mixture = 4.2 kg?1 K?1; Density of water =1.0 gcm?1; Relative atomic masses: K= 39.1, Cl = 35.5) Note that the specific heat capacity of the mixture should be 4.2 kJ kg?1 K?1 or 4.2 J g?1 K?1. Mass of the solution, m = 100 x 1.0 + 10 = 110 g =0.11 kg Heat absorbed = m c ΔT = 0.11 x 4.2 x 5.5 = 2.541kJ No. of moles of KCl used = 10/(39.1 + 35.5) = 0.134 mol Molar enthalpy change = 2.541/0.134 = 18.96 kJ mol?1
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