7.000g of Compound X with molecular formula C3H4 are burned in a constant-pressure calorimeter containing 35.00kg of water at 25 ' C. The temperature of the water is observed to rise by 2.316C. (You may assume all the heat released by the reaction is absorbed by the water, and none by the calorimeter itself.) Calculate the standard heat of formation of Compound X at 25C. Be sure your answer has a unit symbol, if necessary, and round it to 3 significant digits