Consider an apparatus similar to that shown in Figure 14.10, and assume that the
ID: 804872 • Letter: C
Question
Consider an apparatus similar to that shown in Figure 14.10, and assume that the round-bottom flask holds 10 mL and that the distillation head has an internal volume of about 2 mL in the vertical section. At the end of a distillation, vapor would fill this volume, but it could not be forced through the system. No liquid should remain in the distillation flask. Assuming this holdup volume of 12 mL, use the ideal gas law and assume a boiling point of 100 degree Celsius (760 mmHg) to calculate the number of microliters of liquid (d=0.9 g/mL, MW = 200) that would recondense into the distillation flask upon cooling.
Explanation / Answer
1 mole of any gas occupies 22.4 litres at 760 mm Hg and 0 degC.
P = 760, V = 12 ml, T = 100 + 273=373 deg K
Vol at 273 K = 12x 273/373 = 8.783 ml since pressure is 760 at both conditions.
Moles = 8.783/22400 = 3.921e-4
Mass = 3.921 x 200 = 0.0784gms
Volume = mass/density = 0.0784/0.9 = 0.0871 ml