A 2.3 g sample of C5H10O is burned completely in excess oxygen to yield CO2(g) and H2O(l) at 25 C, releasing 83.42 kJ of energy. What is the enthalpy of formation of C5H10O?

Answer 1

What is the DHf for C5H10O?
5C + 5H2 + 1/2 O2 = C5H10O

The combustion reaction is what?
C5H10O + 7O2 ==> 5CO2 + 5H2O
DHf rxn = (5*DHf CO2 + 5*DHf H2O) - (DHf C5H10O)
Look up values for DHf for CO2 and H2O, plug into the equation above with DHf rxn and solve for DHf C5H10O