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 0.4331 g sample of phenanthrene (C_14H_10) is burned completely in a bomb calorimeter. The calorimeter is surrounded by 1.296 times 10^3 g of water. During the combustion the temperature increases from 23.58 to 26.42 degree C. The heat capacity of water is 4.184 J g^-10C^-1. The heat capacity of the calorimeter was determined in a previous experiment to be 794.0 J/degree C. Assuming that no energy is lost to the surroundings, calculate the molar heat of combustion of phenanthrene based on these data. C_14H_10(s) + (33/2) O_2(g) rightarrow 5H_2O (l) + 14CO_2(g) + Energy Molar Heat of Combustion = ____________ kJ/mol

Explanation / Answer

q = m*s*DT

m = mass of water = 1.296*10^3 g

s = specificheat of water = 4.184 j/g.c

DT = 26.42 - 23.58 = 2.84 C

q = 1.296*10^3*4.184*2.84

    = 15.4 kj

DHrxn = q / n

no of mole of C14H1O = W/mwt = 0.4331/178 = 0.0024 mol

DHrxn = 15.4/0.00243 = 6337.45 kj/mol

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