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 1.5720 g sample of fumaric acid (C4H4O4) is burned completely in a bomb calorimeter. The calorimeter is surrounded by 1.239x10^3 g of water. During the combustion the temperature increases from 23.12 to 26.19 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 he 905.4 J/ degree C. Assuming that no energy is lost to the surroundings, calculate the molar heat of combustion of fumaric acid based on these data

Explanation / Answer

Heat gained by water

= mass * specific heat * (change in temperature)

= 1239 * 4.184 * (26.19 - 23.12)

= 15914.86032 = 15.914 KJ

Molar mass of Fumaric acid = 4 * 12 + 4 * 1 + 4 * 16 = 4 * 29 = 116 gm/mol

Number of moles of fumaric acid = 1.5720/Molar mass = 1.5720/116 = 0.01355 moles

Heat of combustion is equal to

-15.914 KJ/0.01355

=> -1176.234 KJ/mol

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