Neco 2024 Chemistry Question 26

An industrial factory discharges wastewater at a rate of \(2000\ \text{L min}^{-1}\) containing nitrate ions \(\text{NO}_{3}^{-}\) at a concentration of \(0.05\ \text{mol L}^{-1}\). A river flows at \(50000\ \text{L min}^{-1}\) with an initial nitrate concentration of \(0.005\ \text{mol L}^{-1}\). The two streams mix completely. The mixed water then passes through a denitrification tank that follows first‑order kinetics with a rate constant \(k = 0.30\ \text{min}^{-1}\) and a hydraulic residence time of \(20\ \text{min}\). (a) Calculate the nitrate concentration (in \(\text{mol L}^{-1}\)) in the water leaving the tank. (b) The environmental standard permits a maximum nitrate concentration of \(0.01\ \text{mol L}^{-1}\). Does the effluent meet the standard?