first question:
how many grams of aluminum chloride is being produced when 1.52 x 10^24 atoms of aluminum react with sufficient amount of chlorine gas?
first use stoichiometry to find aluminum and chlorine react in this way: Al + 3Cl <---> AlCl3 [3 should be subscript]
now realize that aluminum is the limiting reagent (they tell us we get sufficient chlorine). Thus, for every Al atom, we get one Aluminum Chloride molecule.
Thus we will have 1.52 x 10^24 molecules. Now find this molecule's mass in g/mol on the periodic table by combining the required atoms.
Al = 26.982g/mol
Cl = 35.453g/mol
26.982 + 3(35.453) = 133.341 g/mol.
So how many moles do we have? 1 mole = 6.02x10^23, so we just divide our number of molecules by Avagadro's number giving us
(1.52 x 10^24) / (6.02 x 10^23) = 2.52 moles
now multiply 2.52mol x 133.341g/mol = 336.67 grams