Question

What is the standard enthalpy change of combustion (ΔH°c) for propane (C3H8) gas at 298 K, given the balanced chemical equation: C3H8(g) + 5O2(g) -> 3CO2(g) + 4H2O(g)?

Answer 1

To calculate the standard enthalpy change of combustion  Hc  for propane  C3H8  gas at 298 K, we need the standard enthalpies of formation  Hf  for the reactants and products involved in the balanced chemical equation.The balanced chemical equation is:C3H8 g  + 5O2 g  -> 3CO2 g  + 4H2O g The standard enthalpies of formation  Hf  for the substances involved are:Hf [C3H8 g ] = -103.85 kJ/molHf [O2 g ] = 0 kJ/mol  since O2 is in its standard state Hf [CO2 g ] = -393.5 kJ/molHf [H2O g ] = -241.8 kJ/molNow, we can calculate the standard enthalpy change of combustion  Hc  using the following equation:Hc =  [Hf  products ] -  [Hf  reactants ]Hc = [3   -393.5 kJ/mol  + 4   -241.8 kJ/mol ] - [ -103.85 kJ/mol  + 5  0 kJ/mol]Hc =  -1180.5 kJ/mol +  -967.2 kJ/mol   -  -103.85 kJ/mol Hc = -2147.7 kJ/mol + 103.85 kJ/molHc = -2043.85 kJ/molSo, the standard enthalpy change of combustion  Hc  for propane  C3H8  gas at 298 K is approximately -2043.85 kJ/mol.