A tank with a volume of 8 m3 containing 4 m3 of 20% (by volume) NaOH solution is to be purged by adding pure water at a rate of
3 m3/h. The solution leaves the tank at a rate of 2 m3/h. When the tank is full, the solution leave the tank at the same inlet flow of 3 m3/h. Assume perfect mixing. Specific gravity of pure NaOH is 1.22. Determine the time necessary to purge 95% of the NaOH by mass from the tank.
