Question 2B: Q. ll: Aqueous solutions of the amino-acid L-isoleucine (lle) are p

Question

Question 2B:

Q. ll: Aqueous solutions of the amino-acid L-isoleucine (lle) are prepared by putting 100.0 grams of pure water into each of six flasks and adding different precisely weighed quantities of le to each flask. The densities of the solutions at 50.0t0.05°C are then measured with a precision densitometer, with the following results. r (g le/100 g H2O) 0.000 1.7683 2.64 12 3.4093 4.2064 0.8821 p (g solution/cm 0.98803 0.98984 0.99148 0.99297 0.99439 0.99580 (a) Plot a calibration curve showing the mass ratio, r, as a function of solution density, p, and fit a straight line to the data to obtain an equation of the form r a p b (b) The volumetric flow rate of an aqueous lle solution at a temperature of 50 C is 150 L/h. The density of the sample of the stream is measured and found to be 0.9940 g/cm3. Use the calibration equation to estimate the mass flow rate of lle in the stream (in kg lle/h) (c) It has been later discovered that the thermocouple used to measure the stream temperature was poorly calibrated and the temperature was actually 47°C. Would the lle mass flow rate calculated in part (b) be too high or too low?

Explanation / Answer

The equation as suggested is plotted and shown below

The equation to the curve is best represented as r= 545.5*density-539

given density 0.9940 g/cc correspond to 994 g/L

volumetric flow rate= 150 L/ hr and hence mass flow rate= 150*0.994 g solution/ hr=149.1 g/hr solution

from the plot r= glle/H2O= 545.5*0.9940-535.5=3.227 g lle/ 100 gm water H2O

solution mas= 100 gm water and 3.227 g lle

total mass =100+3.227= 103.227 g

103.227 gm solution contains 3.227 gm of lle

149.1 g/hr solution contains 149.1*3.227/103.227 glle/hr=4.66045 glle/hr=0.00466045 kg/hr

since majority of the solution contains water and there wii not be significant change in density of water upon change in temperature, the effect is not that significant.

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