It is thought that corrosion in steam boiler pipes caused by oxygen can be prevented, at least partially, by passing sodium sulfide through the system. Sodium sulfite $(Na2SO3)$ removes oxygen from the boiler feed water.

$2N{a}_{2}S{O}_3+O_{2}2N{a}_{2}S{O}_4$

It is removed by the reaction. Calculate the amount of sodium sulfite in $kg$ required to remove all oxygen from $4000$ tons of feed water containing $10$ ppm dissolved oxygen and at the same time maintain a $35\%$ excess sodium sulfite rate. $425$kgNa $-$ Sulfide