When is it applied? write the equation of a differential mass balance in its most general form showing the notation used. 2 (a) what is a differential mass balance 3 marks] methanol is added to a storage tank containing 900 kg of methanol at a rate of 1500 kg b1 and is simultaneously withdrawn at a rate that increases linearly with time. the initial rate of withdrawal of methanol is 600 kg h1. five hours later the rate of withdrawal equals 1000 kg h- write the general differential mass balance equation applied to the mass of [4 marks] (b) methanol in the tank inserting the values of the parameters given in it. derive an expression for the methanol withdrawal rate as a function of time. (c) (d) (e) ( [3 marks] solve the mass balance equation in 2(b) to obtain an expression for the [3 marks methanol mass in the tank as a function of time. calculate how long it will take for the mass of methanol in the tank to reach its maximum value and calculate that value. 4 marks] calculate the time it will take to empty the tank