The rate constant for a certain reaction is k = 1.50×10?3 s^-1 . If the initial reactant concentration was 0.650M , what will the concentration be after 13.0 minutes? Express your answer with the appropriate units. A zero-order reaction has a constant rate of 1.40×10?4 M/s. If after 40.0 seconds the concentration has dropped to 6.00×10?2 M, what was the initial concentration? Express your answer with the appropriate units