Assume that natural gas is pure CH4 and that the fuel used i

Assume that natural gas is pure CH4 and that the fuel used in gas barbecue grills is pure C3H8.

a) Calculate and compare the energy released by burning 1000 grams of each.

b) Calculate and compare the energy released per mole of CO2 released.

Solution

a) Enthalpy of cumbustion of methane= 890 Kj/mol

=> 16 gm methane give 890 KJ energy

=> 1000 gm methane gives energy = (890/16)*1000= 55625 KJ

Enthalpy of cumbustion of propane= 2220 Kj/mol

=> 42 gm of propane give 2220 KJ of energy

=> 1000 gm propane give energy = (2220/42)*1000=52857.14 KJ

b) CH_4(g) + 2O_2(g) ---> CO_2(g) + 2H₂O_(l)

_{For 1 mol of methane combustion, 1 mol CO2 is relaeased =>} 55625 KJ energy released

C₃H_8(g) + 5O_2(g) ---> 3CO_2(g) + 4H₂O_(l)