First we look at the chemical reaction:
2 Na + Br₂ → 2 NaBr
number of moles = mass / molecular weight
mass = number of moles × molecular weight
number of moles of Na = 1000 / 23 = 43.48 moles
number of moles of Br₂ = 3000 / 160 = 18.75 moles
from the reaction:
if 2 moles of Na are reacting with 1 mole of Br₂
then X moles of Na are reacting with 18.75 moles of Br₂
X = (18.75 × 2) / 1 = 37.5 moles of Na
The limiting reactant is bromine Br₂.
After the reaction is complete you remain with Na as excess reagent.
moles of Na = 43.48 - 37.5 = 5.98 moles
mass of Na = 5.98 × 23 = 137.54 g
if reacting 1 mole of Br₂ produces 2 moles of NaBr
then reacting 18.75 moles of Br₂ produces Y moles of NaBr
Y = (18.75 × 2) / 1 = 37.5 moles of NaBr
mass of NaBr = 37.5 × 103 = 3862.5 g
