A bomb calorimeter, or a constant volume calorimeter, is a device often used to

Question

A bomb calorimeter, or a constant volume calorimeter, is a device often used to determine the heat of combustion of fuels and the energy content of foods. In an experiment, a 0. 3797 g sample of anthracene (C_14H_10) is burned completely in a bomb calorimeter. The calorimeter is surrounded by 1. 137 times 10^3 g of water. During the combustion the temperature increases from 22. 61 to 25. 41 degreeC. The heat capacity of water is 4. 184 Jg^-1degreeC^-1. The heat capacity of the calorimeter was determined in a previous experiment to be 829. 2 J/degreeC. Assuming that no energy is lost to the surroundings, calculate the molar heat of combustion of anthracene based on these data. C_14H_10(s) + (33/2) 0_2(g) rightarrow 5 H_20(1) + 14 C0_2(g) + Energy

Explanation / Answer

Heat absorbed = Qclaorimeter + Qwater = C*dT + m*c*(dT)

dT = 25.41-22.61 = 2.8

Heat absorbed = Qclaorimeter + Qwater = 829.2*2.8 + (1.137*10^3)*4.184*(2.8) = 15641.9424 J

then

HRxn = -Q/n

mol = mass/MW = 0.3797/178.23 = 0.002130

HRxn = -15641.9424 / ( 0.002130) = -7343634.92 J/mol

Hrn = -7343.635 kJ/mol

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