posted by TROUBLED on .
calculate the heat of combustion for the following reactions from the standard enthalpies of formation
2H2(g) + O2(g) = 2H2O(l)
2C2H2(g) + 502(g) = 4CO2(g) + 2 H2O(l)
DHfrxn = (n*DHfproducts) - (n*DHfreactants)
Look up DHf for the material, multiply by n etc.