J.R. S. answered 03/20/22
Ph.D. University Professor with 10+ years Tutoring Experience
In any question of this sort, you must first write the correctly balanced equation for the reaction:
2Na + Cl2 ==> 2NaCl
Next, we must identify the limiting reactant. An easy way to do this is to divided the MOLES of each reactant by the corresponding coefficient in the balanced equation.
For Na: 100.0 g Na x 1 mol Na / 23.0 g = 4.35 mols Na (÷2->2.17)
For Cl2: 12.5 L Cl2 x 1 mol Cl2 / 22.4 L = 0.558 moles Cl2 (÷1->0.56) Recall 1 mol gas @STP = 22.4 L
Since 0.56 is less than 2.17, Cl2 is the limiting reactant.
Now, we use the MOLES of the limiting reactant to find the theoretical yield of the product.
0.558 mols Cl2 x 2 mols NaCl / mol Cl2 x 58.4 g NaCl / mol = 65.2 g g NaCl (3 sig. figs.)