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 1.2550 g sample of glutaric acid (C5H8O4) is burned completely in a bomb calorimeter. The calorimeter is surrounded by 1.367×103 g of water. During the combustion the temperature increases from 27.44 to 30.47 °C. The heat capacity of water is 4.184 J g-1°C-1. The heat capacity of the calorimeter was determined in a previous experiment to be 769.8 J/°C. Assuming that no energy is lost to the surroundings, calculate the molar heat of combustion of glutaric acid based on these data.

C5H8O4(s) + 5O2(g) 4 H2O(l) + 5 CO2(g) + Energy

Molar Heat of Combustion =____________kJ/mol

Explanation / Answer

Heat change = Mass * specific heat * (t2-t1) + heat capacity of calorimeter * ( t2-t1)

q = 1367 * 4.184 * ( 30.47 - 27.44) + 769.8 * ( 30.47 - 27.44)

q = 19663 J

Mass of glutaric acid = 1.2550 g.

Molar mass of glutaric acid = 5(12)+8(1)+4(16) = 132 g/mol

Moles of glutaric acid = mass / molar mass = 1.2550 / 132 = 0.00951 mol

Molar heat of combustion = - q / n = - 19663 / 0.00951 = - 2068140 J/mol = - 2068 kJ/mol = - 2.07 * 10^3 kJ/mol

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