Calculate the heat of formation of propane if the heat of combustion is -2220kj/mol.The heat of formation of carbon (IV) oxide and water are -393.5 and 285.8 kj/mol respectively.
The heat of combustion of propane (C3H8) can be represented by the chemical equation:
C3H8 + 5O2 -> 3CO2 + 4H2O
The heat of formation (ΔHf) of a compound can be related to the heat of combustion (ΔHc) using Hess's Law:
ΔHc = Σ(ΔHf products) - Σ(ΔHf reactants)
In this case, the ΔHc of propane is given as -2220 kJ/mol, and the ΔHf values of CO2 and H2O are given as -393.5 kJ/mol and -285.8 kJ/mol, respectively. The ΔHf of O2 can be taken as 0 since it's an element in its standard state.
Now we can plug in the values into the equation:
-2220 = (3*(-393.5) + 4*(-285.8)) - (ΔHf(C3H8) + 5*0)
-2220 = (-1180.5 - 1143.2) - ΔHf(C3H8)
-2220 = -2323.7 - ΔHf(C3H8)
Next, we solve for the heat of formation of propane (ΔHf(C3H8)):
ΔHf(C3H8) = -2323.7 + 2220
ΔHf(C3H8) = 103.7 kJ/mol
Therefore, the heat of formation of propane is 103.7 kJ/mol.