The standard heat of combustion ( AH, ) of liquid 2,3,3-trimethylpentane [C3H18] is reported in a...

 

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The standard heat of combustion ( AH, ) of liquid 2,3,3-trimethylpentane [C3H18] is reported in a table of physical properties to be -4850.0 kJ/mol. A footnote indicates that the reference temperature for the reported value is 25°C and the presumed combustion products are CO2(g) and H20(g). The heat capacity of water is approximately 75.40 J/(mol K) over the temperature range of interest. Physical Property Tables Heat of Combustion There is some question about the accuracy of the reported value, and you have been asked to determine the heat of combustion experimentally. You burn 2.030 grams of the hydrocarbon with pure oxygen in a constant-volume calorimeter and find that the net heat released when the reactants and products [CO2(g) and H20(g)] are all at 25°C is sufficient to raise the temperature of 1.000 kg of liquid water by 20.84 °C. Write an energy balance to show that the heat released in the calorimeter equals nc, Hs and calculate AU. (k)/mol). kJ/mol Then calculate AH . (See Example 9.1-2.) kJ/mol Heat of Formation A° Use the result for the measured (not the tabulated value) heat of combustion to estimate AH, for 2,3,3-trimethylpentane. kJ/mol the tolerance is +/-9% The standard heat of combustion ( AH, ) of liquid 2,3,3-trimethylpentane [C3H18] is reported in a table of physical properties to be -4850.0 kJ/mol. A footnote indicates that the reference temperature for the reported value is 25°C and the presumed combustion products are CO2(g) and H20(g). The heat capacity of water is approximately 75.40 J/(mol K) over the temperature range of interest. Physical Property Tables Heat of Combustion There is some question about the accuracy of the reported value, and you have been asked to determine the heat of combustion experimentally. You burn 2.030 grams of the hydrocarbon with pure oxygen in a constant-volume calorimeter and find that the net heat released when the reactants and products [CO2(g) and H20(g)] are all at 25°C is sufficient to raise the temperature of 1.000 kg of liquid water by 20.84 °C. Write an energy balance to show that the heat released in the calorimeter equals nc, Hs and calculate AU. (k)/mol). kJ/mol Then calculate AH . (See Example 9.1-2.) kJ/mol Heat of Formation A° Use the result for the measured (not the tabulated value) heat of combustion to estimate AH, for 2,3,3-trimethylpentane. kJ/mol the tolerance is +/-9%