If 6.5g of zinc react with 5.0g of HCl which subance is the limiting reactant? How many gram of the reactant remaint unreacted? How many gram of hydrogen would be produced?
Zn + 2HCl ==> ZnCl2 + H2
mols Zn = 6.5/65.4 = 0.0994
moles HCl = 5.0/36.5 = 0.137
If all of the 0.0994 mols Zn react how much HCl will be required? That's 0.0994 x 2 = 0.199. You don't have much HCl; therefore, HCl is the limiting reagent (LR) and Zn is the excess regent (ER).
b) moles Zn required to react with all of the HCl = 0.137 x (1 mol Zn/2 mols HCl) = 0.137 x 1/2 = 0.0685. So you will have left 0.0994 - 0.0685 = ? moles Zn and grams Zn = moles Zn x atomic mass Zn = ?
c) moles H2 produced = 0.137 moles HCl x (1 mol H2/2 mols HCl) = 0.137 x (1/2) = 0.0685. Then grams H2 = moles H2 x molar mass H2 = ?