A 35.6 g sample of ethanol (C₂H₅OH)is burned in a bomb calorimeter according to the following reaction.If the temperature rose from 35.0 °C to 76.0°C and the heat capacity of the calorimeter is 23.3 kJ ${ } ^ { \circ } \mathrm { C } ^ { - 1 }$ ,what is the value of $\mathrm { D } _ { \mathrm { r } } U ^ { \circ }$? The molar mass of ethanol is 46.07 g $\mathrm { mol } ^ { - 1 }$ . C₂H₅OH(l)+ 3O₂(g)? 2CO₂(g)+ 3H₂O(g) $\mathrm { D } _ { \mathrm { r } } U ^ { \circ }$= ?

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Quizplus · Accepted Answer

The heat absorbed by the calorimeter is calculated using q = C × ΔT = 23.3 kJ/°C × (76.0°C - 35.0°C) = 955.9 kJ. The number of moles of ethanol is 35.6 g / 46.07 g/mol = 0.772 moles. The change in internal energy per mole is ΔU = q / moles = 955.9 kJ / 0.772 mol = -1.24 × 10^3 kJ/mol. The negative sign indicates that the reaction is exothermic.

A 356 G Sample of Ethanol (C2H5OH)is Burned in a Bomb

A 356 G Sample of Ethanol (C₂H₅OH)is Burned in a Bomb