8. A student conducts an experiment to determine the enthalpy of solution for li

Question

8. A student conducts an experiment to determine the enthalpy of solution for lithium chloride dissolved in water. The student combines 5.00 grams of lithium chloride with 100.0 mL of distilled water. The initial temperature of the water is 23.0°C and the highest temperature after mixing reaches 33.00. Assume a density of 1 .00 gmL and a specific heat of 4.18 JgoC. The calorimeter constant was found to be 20.0 J/°C a. Is the reaction endothermic or exothermic? Justify your answer b. Calculate the temperature change of the solution in the calorimeter. c. Calculate the total mass of the solution in the calorimeter d. Calculate the energy change of the solution. e. Calculate the energy change of the calorimeter f. Calculate the total "-inkl mole 430 Copyright© 2017 National Math + Scienceintiative, Dallas, Texas. All rights reserved. Vist us online at www nms or

Explanation / Answer

a) Endothermic reaction as the heat is absorbed in water

b) Change in Temperature of the solution in the Calorimeter = 33 oC - 23 oC = 10 oC

c) Total mass of the solution in the calorimeter = 5g of Lithium Chloride + 100 mL * 1g/mL (Mass = volume*density) = 105 g

d) The Energy change in the solution = 4.18 J/goC *  10oC *(105g/60.4g/mol) = 72.66 J/mol or 0.07266 KJ/mol

e) The Energy change in the calorimeter = 20J/oC * 10oC *(105g/60.4g/mol) (Molar mass of Solution = LiCl + Water = 42.39 g/mol +18.01 g/mol = 60.40g/mol)

The Energy change in the calorimeter = 20J/oC * 10oC *(105g/60.4g/mol) = 347.68 J/mol or 0.3476 KJ/mol

f) Total Hsolution = 0.07266 KJ/mol + 0.3476 KJ/mol = 0.4203 KJ/mol

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