When 0.627 g of biphenyl (CH) combusts in a bomb calorimeter, the temperature rises from 21.9 C to 26.6 C. What is U for the reaction in kJ/mol biphenyl

Explanation:

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In this case, since the heat capacity of the bomb calorimeter, we can use this found value on ethernet: 5.86 kJ/°C, thus, we can compute the heat gained by the calorimeter:

Thus, since the heat gained by the calorimeter is actually the heat released due to the combustion of byphenyl, we compute it as the negative of that of the calorimeter:

Finally the energy of reaction, U, in kJ/mol for the combustion of byphenyl (molar mass = 154 g/mol) is:

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c-14 is carbon-14, or radiocarbon.   it is a radioactive isotope of carbon with an atomic nucleus containing 6 protons and 8 neutrons.