First, we need to get the moles of Cl2 ( chlorine)
we can use the ideal gas formula to get n ( moles of gas) :
PV = nRT
when p is the pressure = 1.3 atm
and V is the volume = 25.8 L
R is the constant of the ideal gas = 8.314
T temperature in Kelvin = 293
∴ n = PV / RT
= 1.3 * 25.8 / 8.314* 293
= 0.0138 moles
according to the reaction equation:
2Na(s) +Cl2 → 2 NaCl
we can see from the balanced equation that the molar ration between Na & Cl2 = 2: 1
∴ moles of Na = moles of Cl2 / 2
= 0.0138 / 2
= 0.0069 moles
now, we have the moles of Na and by using the molar mass of Na = 22.99 g/mol
∴ Mass of Na = moles of Na * molar mass
= 0.0069 moles * 22.99
= 0.1586 g