Consider the combustion of propane gas, Propane is often used for gas grills and
ID: 534754 • Letter: C
Question
Consider the combustion of propane gas,
Propane is often used for gas grills and is typically purchased by filling a propane tank with 20 pounds of propane. What is the enthalpy change when 3 pound of propane is burned? Use the conversion 1 lb = 454 g and express your answer in scientific notation. For example use 2.3e-5 to indicate a number such as 2.3 x 10-5.
kJ
What is the enthalpy change for
Hint, compare this equation to the combustion equation for propane.
kJ
C3H8(g) + 5O2(g) 3CO2(g) + 4H2O(l) Ho = -2,220 kJ/molExplanation / Answer
Molar mass of propane = 44.1 g / mol
3 pounds or 3 x 454 g = 1362 g = 1362 / 44.1 = 30.9 moles of propane.
The enthalpy change associated with the combustion of 1 mole of propane = -2220 KJ/ mol , so enthalpy change with that of 30 .9 moles = 30.9 x -2220 KJ = -68598 KJ
So the enthalpy change = -6.8e4 KJ
The enthalpy change for the reaction , 6CO2 + 8H2O = 2C3H8 + 10O2, will be twice of the reverse reaction for the combustion of propane , i.e.
2 x - (-2220) = +4440 KJ
= 4440 KJ