Answer how many moles of sodium will react with 2.6l of cl2 gas at 1.15 atm

The chemical equation for the reaction is ,

                                      2 Na  +  Cl₂     →     2 NaCl

Before applying stoichiometry, first you will have to find the moles of Cl₂ at given conditions using Ideal gas equation.

                                        n  =  P V / R T

As, temperature is not given, so put standard Temperature i.e. 273 K, or if you are provided with it simply put its value So,

               n  =  (1.15 atm × 2.6 L) ÷ (0.0821 atm.L.mol⁻¹.K⁻¹ × 273 K)

               n  =  0.133 mol of Cl₂
Now,
According to Balance equation,

                          1 mole Cl₂ required  =  2 moles of Na
So,
                 0.133 mol Cl₂ will require  =  X moles of Na

Solving for X,
                             X  =  (0.133 mol × 2 mol) ÷ 1 mol

                             X  =  0.266 moles of Na

The density would be 1.622