The reaction that is given in this item is written below,
2Na + Cl2 --> 2NaCl
From the equation, it can be seen that for every mole of sodium, it would require 1 mol of Cl2 for the complete reaction. Below is the calculation of the number of moles of chlorine.
n = (2 mol Na)(1 mol Cl2/2 mol Na) = 1 mol Cl2
The molar mass of Cl is equal to 35.45 grams. Since, we have Cl2, the mass of the chlorine gas needed would be 70.9 grams.
Answer: 70.9 grams