From 2HCl(aq) + ZnS(s) ---------> H2S (g) + ZnCl2 (aq)
From the reaction equation;
2 moles of HCl produces 1 mole of H2S
Therefore 2.25 moles of HCl will produce 2.25 ×1/2 = 1.125 moles of H2S
Recall that it was explicitly stated in the question that ZnS is the reactant in excess. This implies that HCl is the limiting reactant and controls the amount of product obtained.
scientific notation is about how many places passed the decimial place you are moving. therefor in order to get 1,550,000,000 you would move the decimial from 1.55 over nine times to the right
