2. One hundred fifty kmol of an aqueous phosphoric acid solution contains 5.00mole2H3PO4. The solution is concentrated by adding pure phosphoric acid at a rate of 20.0L/min. a. Write a differential mole balance on phosphoric acid and provide an initial condition. [Start by defining np ( kmol ) to be the total quantity of phosphoric acid in the tank at any time.] Without solving the equation, sketch a plot of np versus t and explain your reasoning. b. Solve the balance to obtain an expression for np(t). Use the result to derive an expression for xp(t), the mole fraction of phosphoric acid in the solution. Without doing any numerical calculations, sketch a plot of xp versus t from t=0 to t, labelling the initial and asymptotic values of xp on the plot. Explain your reasoning. c. How long will it take to concentrate the solution to 15%H3PO4