homework help

Question

When 0.594 g of biphenyl (C12H10) undergoes combustion in a bomb calorimeter, the temperature rises from 25.3 ∘C to 30.0 ∘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.

Answer 1

q = C_cal∆T

q = heat = ?

C_cal = 5.86 kJ/deg (are you sure it isn't 5.86 J/deg?)

∆T = change in temp = 30.0 - 25.3 deg = 4.7 deg

q = (5.86 kJ/deg)(4.7 deg) = 27.5 kJ

molar mass biphenyl = 144 + 10 = 154 g/mol

moles biphenyl combusted = 0.594 g x 1 mol/154 g = 0.00386 moles

∆Erxn = 27.5 kJ/0.00386 moles = 71214 kJ

This seems very high.  You may check on the actual value of C_cal