TABLE OF CONTENTS James R.Beckman, Ph.D.
Associate Professor and Associate Chair
Department of Chemical and Materials Engineering
Arizona State University
Tempe, AZ
A 65.2 wt % aqueous solution of potassium nitrate originally at 100 C (212 F) is gradually cooled to 10 C (50 F). What is the yield of KNO 3 solids as a function of temperature? How many pounds of KNO 3 solids are produced at 10 C if the original solution weighed 50,000 lb (22,680 kg)?
1. Convert weight percent to mole percent. In order to use Fig. 10.1 in the next step, the mole fraction of KNO 3 in the original solution must be determined. The calculations are as follows:
| Compound | Pounds in original solution | Molecular weight | = | Moles | Mole percent | |
|---|---|---|---|---|---|---|
| KNO 3 | 0.652 |
| 101.1 |
| 0.00645 | 25.0 |
| H 2O | 0.348 |
| 18.0 |
| 0.01933 | 75.0 |
| Total | 1.000 |
|
|
| 0.02578 | 100.0% |
2. Calculate yield of solids versus tempera ture. Figure 10.1 shows the composition of saturated KNO 3 solution as a function of temperature. The solids formed during cooling will be 100 percent KNO 3, because KNO 3 is anhydrous. The yield of solids is the ratio of KNO 3 solidified to the KNO 3 originally dissolved. As can be seen from Fig. 10.1, no solids are formed from a 25 mol...
