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 0.5078 g sample of benzoic acid (C_7 H_6 O_2) is burned completely in a bomb calorimeter. The calorimeter is surrounded by 1.214 times 10^3 g of water. During the combustion the temperature increases from 26.23 to 28.55 degree C. The heat capacity of water is 4.184 J g^-1 degree C^-1. The heat capacity of the calorimeter was determined in a previous experiment to be 964.9 J/degree C. Assuming that no energy is lost to the surroundings, calculate the molar heat of combustion of benzoic acid based on these data. C_7 H_6 O_2 (s) + (15/2) O_2 (g) rightarrow 3 H_2 O (1) + 7 CO_2 (g) + Energy Molar Heat of Combustion = kJ/mol

Explanation / Answer

no of mole of benzoicacid = w/mwt = 0.5078/122.12 = 0.00416 mole

heat released during the process(q) = m*s*DT + C*DT

                  m = mass of water = 1.214*10^3 g

                  s = specific heat of water = 4.184 j/g.c

                  DT = 28.55 - 26.23 = 2.32

                  C = heat capacity of clorimeter = 964.9 j/c

       q = 1.214*10^3*4.184*2.32 + 964.9*2.32

          = 14022.72 joule

          = 14.022 kj

enthalpy of combustion(DHrxn) = - q/n

                               = - (14.022/0.00416)

                               = -3370.67 kj/mole

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