Answer :
Grams of Cl₂ needed : 71.781 g
Further explanation
Reaction
2 Na + Cl₂ → 2 NaCl
mass of Na = 46.5 g
mol of Na(Ar=23 g/mol) :
[tex]\tt mol=\dfrac{mass}{MW}\\\\mol=\dfrac{46.5}{23}=2.021[/tex]
From equation, mol ratio of Na : Cl₂ = 2 : 1, so mol Cl₂ :
[tex]\tt \dfrac{1}{2}\times 2.021=1.011[/tex]
Mass of Cl₂(MW=71 g/mol) :
[tex]\tt mass=mol\times MW\\\\mass=1.011\times 71\\\\mass=71.781~g[/tex]