Thermodynamics

Thermodynamics

Question

For the complete combustion of ethanol, C2H5OH (l) + 3O2 (g) → 2CO2 (g) + 3H2(l), the amount of heat produced as measured in a bomb calorimeter, is 1364.47 kJ mol-1 at 25oC. Assuming ideality the enthalpy of combustion, CH, for the reaction will be (R = 8.314 JK-1 mol-1)

  • -1366.95 kJ mol-1

  • -1361.95 kJ mol-1

  • -1460.50 kJ mol-1

  • -1350.50 kJ mol-1

Answer

A.

-1366.95 kJ mol-1

C2H5OH (l) + 3O2 (g) → 2CO2 (g) + 3H2(l),
∆U = - 1364.47 kJ/mol
∆H = ∆U +∆ngRT
∆ng = -1
∆H = - 1364.47 +fraction numerator negative 1 space straight x space 8.314 space straight x space 298 over denominator 1000 end fraction
[Here, value of R in unit of J must be converted into kJ]
 = - 1364.47-2.4776
 = -1366.94 kJ/mol

More Chapters from Thermodynamics