First balance the equation with the following coefficients respectively: 2 2 1
This is solved by subtracting the summation of the stoichiometric coefficient of the products multiplied by the heat of formation and the summation of the stoichiometric coefficient of the reactant multiplied by the heat of formation of the certain specie.
1(0)+2(0) - (2)(-90.83) = 181.66 or 182 J
