4. The P-T phase diagram of water is shown below: critical point 220 Solid (Ice)

Question

4. The P-T phase diagram of water is shown below: critical point 220 Solid (Ice) Liquid Protein solution 1.0 Gas (water vapor) e 0.006 0.005 Triple point 0.001 273 298 587 T (K) a. Use the diagram to illustrate the process you would use to lyophilize (freeze dry) a protein solution. You are provided liquid nitrogen, a lyophilizer with a cold trap and a vacuum pump that can reduce pressure down to 0.001 bar, and a water bath for heating and cooling of the protein solution in the process. b. In the middle of the process, the cold trap sort of failed and too much water got into the vacuum pump and the pressure could only go down to 0.005 bar. What would you do to ensure that the process could be continued to completion? Hint: think about how to remove water while keeping the solution frozen (in solid form).

Explanation / Answer

a)

step1:- reduce the temp. of the protein from 298 to well below 273.

           Now protein will be in solid form.

step2;- reduce the pressure upto 0.001 bar.

now our system is below critical points of the water.

step3:- now increase the temp. at constant pressure, so the process will intersect the sublimation line and moisture will get vaporised.

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