Question

Bomb calorimetry is a technique used to determine the enthalpy of combustion, usually in O2, of a chemical species. A known amount of compound is placed inside a fixed volume container that is, in turn, filled with oxygen at a high enough pressure to ensure complete combustion. The fixed-volume container (the 'bomb') is then inserted into a bucket containing a precisely known volume of water. The oxygen and compound are ignited, and the temperature change in the water is recorded. All heat is transferred to the water, and the temperature of the reaction itself is considered to be constant at some stated temperature, such as 298 K. If the water temperature increases, the reaction is exothermic, and if the water temperature decreases, the reaction is endothermic. en the wotis exothermc In the first part of the experiment, a known quantity of benzoic acid undergoes combustion in the calorimeter. The temperature change is recorded, and the heat capacity of the calorimeter is determined using the known energy of combustion of benzoic acid, 26.43 kJ/g. In the second part of the experiment, a known quantity of a compound is then combusted and the temperature change recorded. Using the previously determined Ccal, the energy of combustion of the compound is calculated. For additional information look up bomb calorimetry in your textbook (the problem is fully worked out) or go to this link (or enter http://web.mst.edu/gbert/animation.html in your browser address line), which is an excellent animation of the use of a bomb calorimeter to determine enthalpy of combustion. Please note that in the problem below we neglect the enthalpy of combustion of the nichrome wire in our calculations. A sample of benzoic acid of mass 0.5354 g undergoes combustion in a bomb calorimeter. The temperature increases by 1.669 °C. Next, a sample of some unknown sugar of mass 0.7980 g undergoes combustion in this bomb calorimeter. The temperature increases by 0.101 °C. The sugar has a molar mass of 152.58 g mol1. What is the molar internal energy of combustion of the sugar in kJ mol? kJ mol- Submit Answer Tries 0/3 The combustion of this sugar consumes 3 moles oxygen gas and yields 6 moles carbon dioxide gas per "mole" of reaction. What is the molar enthalpy of combustion of the sugar in kJ mol1 at 298 K? k) mol-1 Submit Answer Tries 0/3

Answer 1