3.21. WP Liquid toluene is flowing through a pipe at a rate of 175 m³/h. a. What is the mass flow rate of this stream in kg/min? b. What is the molar flow rate in mol/s? c. In fact, the answer to Part (a) is only an approximation that is almost certain to be slightly in error. What did you have to assume to obtain the answer? 3.22. WP A mixture of methanol and propyl acetate contains 25.0 wt% methanol. a. Using a single dimensional equation, determine the g-moles of methanol in 200.0 kg of the mixture. b. The flow rate of propyl acetate in the mixture is to be 100.0 lb-mole/h. What must the mixture flow rate be in lbm/h? > Answer 3.23. WP The feed to an ammonia synthesis reactor contains 25 mole% nitrogen and the balance hydrogen. The flow rate of the stream is 3000 kg/h. Calculate the rate of flow of nitrogen into the reactor in kg/h. (Suggestion: First calculate the average molecular weight of the mixture.) 3.24. WP As described in Problem 3.16, a drilling mud is a slurry pumped into oil wells being drilled. The mud has several functions: It floats rock cuttings to the top of the well where they can easily be removed; lubricates and cools the drill bit; and keeps loose solids and water from leaking into the borehole. A drilling mud is prepared by blending barite (SG = 4.37) with seawater (SG = 1.03) . The seawater has a dissolved salt content of approximately 3.5 wt%. You have been asked to determine the specific gravity of the mud and the wt% barite. You collect a sample of the mud from a blending tank on an oil platform and make the following observations: (i) The mud appears homogeneous, even after standing for 2 days; (ii) the tare mass of the calibrated vessel into which you pour the sample of mud is 118 g; (iii) the volume of the collected sample is 100 mL, and the mass of the collection vessel and sample is 323 g; and (iv) the mass of the vessel and residue remaining after completely evaporating water from the sample is 254 g. a. Estimate the specific gravity of the mud and the wt% barite. Answer b. What is the practical importance of Observation (i)? 3.25. WP Amixture is 10.0 mole% methyl alcohol, 75.0 mole% methyl acetate (C,H602), and 15.0 mole% acetic acid. Calculate the mass fractions of each compound. What is the average molecular weight of the mixture? What would be the mass (kg) of a sample containing 25.0 kmol of methyl acetate? ENVIRONMENTAL 3.26. WP Certain solid substances, known as hydrated compounds, have well-defined molecular ratios of water to some other species. For example, calcium sulfate dihydrate (commonly known as gypsum, CaSO4:2H,O), has 2 moles of water per mole of calcium sulfate; alternatively, it may be said that 1 mole of gypsum consists of 1 mole of calcium sulfate and 2 moles of water. The water in such substances is called water of hydration. (More information about hydrated salts is given in Chapter 6.) In order to eliminate the discharge of sulfuric acid into the environment, a process has been developed in which the acid is reacted with aragonite (CaCO2) to produce calcium sulfate. The calcium sulfate then comes out of solution in a crystallizer to form a slurry (a suspension of solid particles in a liquid) of solid gypsum particles suspended in an aqueous CaSO4 solution. The slurry flows from the crystallizer to a filter in which the particles are collected as a filter cake. The filter cake, which is 95.0 wt% solid gypsum and the remainder CaSO4 solution, is fed to a dryer in which all water (including the water of hydration in the crystals) is driven off to yield anhydrous (water-free) CaSO, as product. A flowchart and relevant process data are given below.