Problem: a. Write a balanced equation for the combustion of ethanol, C2H5OH(l) in oxygen. Carbon dioxide is produced in the gaseous state, water in the liquid state.b.The standard heat of combustion of ethanol is -1367 kJ/mol. Calculate the standard heat of formation of ethanol, ΔH.

a. Combustion  → carbon dioxide is produced in the gaseous state, water in the liquid state

Combustion reaction:

C₂H₅OH(l) + O₂(g) → CO₂(g) + H₂O(l)

Balance C:

C₂H₅OH(l) + O₂(g) → 2 CO₂(g) + H₂O(l)

Balance H:

C₂H₅OH(l) + O₂(g) → 2 CO₂(g) + 3 H₂O(l)

Balance O:

C₂H₅OH(l) + 3 O₂(g) → 2 CO₂(g) + 3 H₂O(l)

Balanced reaction:  C₂H₅OH(l) + 3 O₂(g) → 2 CO₂(g) + 3 H₂O(l)

b. 

$\boxed{\mathbf{\Delta H}{\mathbf{°}}_{\mathbf{rxn}}\mathbf{=}\mathbf{\Delta H}{\mathbf{°}}_{\mathbf{f}\mathbf{,}\mathbf{ }\mathbf{prod}}\mathbf{-}\mathbf{\Delta H}{\mathbf{°}}_{\mathbf{f}\mathbf{,}\mathbf{ }\mathbf{react}}}$

ΔH°_f can be found in books or the internet