Question

Consider the three fuels burned to produce energy: natural gas(primarily methane (CH4)), fuel oil (primarily dodecane (C12H25)),and coal (primarily graphite (C)).

Name Substance Formula M (g/mol) ?fHo (kJ/mol)

------- --------- --------- --------- --------
Natural gas, methane CH4(g) 16.04 -74.81
Fuel oil, dodecane C12H26(l)170.34 -353.50
Coal, graphiteC(s) 12.01 0.00

a) If the reaction is carried out atconstant temperature and
pressure, find the heat generated per unit mass in the combustionof each fuel
in (MJ/kg of fuel) and in (kBtu/lb of fuel).
This is what is known as the higher heating value (HHV) of thefuel
since the product water is not vaporized.

you may need to calculate the enthalpy of combustion for eachfuel.

b) Given the prices for these fuels (natural gas--$0.53/ccf at STP,fuel oil--$3.04/gal, coal--$82.00/ton), calculate the energy costof each fuel in ($/GJ). Which fuel is most cost effective? (Assumemethane is ideal, Vm(STP) = 22.414 L, and ?dodecane = 0.750g/mL)

Useful information:


1 MJ = 1 x 106 J
1 GJ = 1 x 109 J
1 Btu = 1055 J
1 lb = 453.59 g
1 ccf = 100 ft3

1 ft = 12 in
1 in = 2.54 cm
1 L = 1000 cm3
1 gal = 3785 mL
1 cm3 = 1 mL
1 ton = 2000 lb
1 kg = 1000 g
1 kBtu = 1000 Btu