Final answer:
The calculation of internal energy of combustion for the biphenyl cannot be completed without the calorimeter's specific heat capacity.
Step-by-step explanation:
To determine the internal energy (ΔU) of combustion for the biphenyl in a bomb calorimeter, we use the calorimeter's heat capacity (Ccal) and the temperature change (ΔT).
As the specific heat capacity is not provided for biphenyl, we cannot complete the calculation without additional data. However, the standard approach to such a problem requires using the formula ΔU = Ccal ΔT.
The combustion of benzoic acid in a bomb calorimeter typically helps to determine Ccal, as benzoic acid has a known enthalpy of combustion (ΔHcomb = -26.38 kJ/g).
The temperature rise and the known ΔHcomb of a standard are used to calculate Ccal, which can then be applied to the unknown substance being tested.
Normally, benzoic acid's known enthalpy of combustion helps calculate the calorimeter's heat capacity, which is then used to find the internal energy for the tested substance.