Question

When 0.612 g of biphenyl (C12H10) undergoes combustion in a bomb calorimeter, the temperature rises from 26.6 ∘C to 29.5 ∘C .

Find ΔErxn for the combustion of biphenyl in kJ/mol biphenyl. The heat capacity of the bomb calorimeter, determined in a separate experiment, is 5.86 kJ/∘C .

ΔErxn =

Answer 1

From the question, we have Mass (m) of C12H10 Molecular mass (M) of C17H10 is = 154 g/mol Change in temperature ( Δ T)-(29.5-26.6) o C-29°C Heat capacity (C) 5.86 kJ/ The number of moles of biphenyl (C1^H10) is calculated as follows: Number of moles of CtH1o (n) - m/M 0.612 g/ 154 g/mol 0.00397 mol The heat evolved is given bv, = 0.612 g * 5.86 kJ/C * 2.9 °C - 10.4 KJ In a bomb calorimeter the amount of heat released due to reaction - heat absorbed by the calorimeter therefore, calorimeter or 10.4 KJ- - 10.4 KJ The AEn is calculated by dividing heat evolved by number of moles of C12H10 as follows: /n xn calorimeter'1 10.4 KJ/0.00397 mol - - 2619.72 KJ/mol