A mercury mirror forms inside a test tube by the thermal decomposition of mercury(II) oxide. 2 HgO(s)-----> 2 Hg(l) + O2(g) delta H rxn = 181.6 kJ (a) How much heat is needed to decompose 505 g of the oxide? ...... kJ (b) If 268 kJ of heat is absorbed, how many grams of mercury form?