Mercury is a toxic heavy metal which is liquid at room temperature. To form HgBr2, mercury(II) bromide, a student reacts elemental bromine with elemental mercury. If the reaction vessel contains 104.833 g of Hg, and the student adds 7.911 g of bromine, has the student added enough bromine to completely react with the Hg? How much of the reactant that was not used up all the way is left?