How many liters of nitrogen gas are needed to make 25 mol of nitrogen trifluoride

The reaction between N₂ and F₂ gives Nitrogen trifluoride as the product. The balanced equation is;

N₂ + 3F₂ → 2NF₃

The stoichiometric ratio between N₂ and NF₃ is 1 : 2
Hence, 
  moles of N₂ / moles of F₂ = 1 / 2
  moles of N₂ / 25 mol        =  0.5
           moles of N₂            =  0.5 x 25 mol = 12.5 mol
 
Hence N₂ moles needed  = 12.5 mol

At STP (273 K and 1 atm) 1 mol of gas = 22.4 L

Hence needed N₂ volume = 22.4 L mol⁻¹ x 12.5 mol
                                          = 280 L