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

Question

A bomb calorimeter, or constant volume calorimeter, is a device often used to determine the heat of combustion of fuels and the energy content of foods. Since the "bomb" itself can absorb energy, a separate experiment is needed to determine the heat capacity of the calorimeter. This is known as calibrating the calorimeter. In the laboratory a student burns a 0.424-g sample of 9,10- anthracenedione (C_14 H_8 O_2) in a bomb calorimeter containing 1100, g of water. The temperature increases from 24.90 degree C to 27.30 degree C. The heat capacity of water is 4.184 J g^-1 degree C^-1. The molar heat of combustion is -6464 kJ per mole of 9,10-anthracenedione. C_14 H_8 O_2(s) + 15 O_2 (g) rightarrow 14 CO_2 (g) 4 H_2 O(l) + Energy Calculate the heat capacity of the calorimeter. heat capacity of calorimeter = _____ J/degree C

Explanation / Answer

Molar mass of C14H8O2 = 14(12) + 8(1) + 2 (16) = 208 g/mol

Mass of C14H8O2 = 0.424 g.

Number of moles of C14H8O2 = 0.424 / 208 = 0.00204 mol

Heat of combustion of 0.00204 mol of C14H8O2 = - 6464 * 0.00204 = - 13.2 kJ

We know that,

Heat of combustion = heat capacity of calorimeter + heat change of water

- 13.2 = Ccal - 1100*4.184*(27.30 - 24.90)

Ccal = 11032.6 J/0C

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