The reaction between chlorine gas (Cl2) and potassium (K) in order to form potassium chloride (KCl) is written below.
2K + Cl2 à 2KCl
We are to calculate the amount of product produce per given mass of reactant.
(7 g of chlorine gas)
(7 g Cl2) x (1 mol Cl2/70.90 g Cl2) x (2 mol KCl/1 mol Cl2) = 0.197 mols Cl2
(5 g of potassium)
(5 g K) x (1 mol K/39.10 g K) x (2 mol KCl/2 mol K) = 0.127 mols Cl2
Since, the calculate mols of Cl2 for 5 g of potassium is lesser then, the limiting reactant is potassium.