± calorimetry Constants Periodic Table Part A calorimeter is an insulated device

Question

± calorimetry Constants Periodic Table Part A calorimeter is an insulated device in which a chemical reaction is contained. By measuring the temperature change, AT we can cacuiate the heat released or absorbed during the reacion using the tollowing equation A calormeter contains 320 mL of water at 15 g/mol ) is added it dissolves wa the reaction C When 2 30 g of X (a substance with a molar mass of 820 and the temperature of the solution increases to 295 °C Calculate the enthalpy change, H·for hs eacon per mole of X Assume that the specific heat of the cesulting solution is equal to that of water 14 18J/g s 100 g/mL and that no heat is lost to the calorimeter itselt, nor to the surroundings Express the change in enthalpy in kilojoules per mole to three significant figures iew Avaitable Hints specific heat × mass × ar Or, if the calorimeter has a predetermined heat capacity, C. the equation becomes "C)j, that density of water At constant pressure the enthalpy change tor the reaction, H s equal to the heat %-thit but it is usually expressed per mole of reactant and with a sign opposne to that of g for the surroundings the total 'tenal energy charge. (sonntimes referred to as 1/1-the sum of heat. g and work done,w 0 kJ/mol However, at constant volurme (as wih a bomb calorimeter) 0 and so E . Submit

Explanation / Answer

B)

The heat produced in a bomb calorimeter when combusting a given amount of known substance is the internal energy of the substance combusted per the number of moles of the substance that was burned.

Here 10.0 g of sucrose is (10.0 g of sucrose) / (342.3 g/mol) = 0.02921 moles of sucrose

You are given that the heat capacity of the calorimeter is 7.50 kJ/ deg C. This means that the temperature of calorimeter increases 1 deg C when 7.50 kJ of heat is absorbed by the calorimeter from the combustion process. Since the temperature increase was 22.0 deg C when combusting the 0.02921 moles of sucrose, then the combustion process must have given off (22.0 deg C)(7.50 kJ/deg C) = 165.0 kJ..

Therefore, the change in internal energy per mole of sucrose combusted would be = (165.0 kJ) / (0.02921 moles of sucrose combusted) = 5649 kJ/mol of sucrose combusted

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