The specific heat of an unknown element in the solid, liquid and gas phases are 100, 50 and 2.5 J/g C. the heat of vaporization is 105kJ/mol. the heat of fusion is 216 kJ/mol, and the molar mass of the unknown solid is 168g/mol. how much heat is needed to melt 1050g of the unknown at 510k. the melting point of the solis unknown is 670k and the boilding point is 800k.