HW #12‐CHEN 354‐Due Friday, April 23, 2010
Problem 1. A 50 wt% (22.5 mol%) solution of ethylene‐glycol and water freezes at 240 K.
What freezing temperature would be predicted by assuming that ethylene glycol and water form
an ideal solution? The freezing occurs by formation of water crystals.
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Problem 2. Estimate the solubility of naphthalene (1) in nitrogen (2) at 35 C at pressures up to 300 bar.
Use the procedure in section 14.7 with l12 =0, and l12 =0.05 . Compare the results with those in Fig. 14.23
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for naphthalene/CO2 at 35 C with l12 =0 and l12 =0.088. Discuss any differences.
Problem 3. A liquid mixture of benzene and n‐heptane is to be cooled to a temperature as low as
possible without precipitation of a solid phase. If the solution contains 10 mol% benzene, estimate what
this lowest temperature is. Solids are immiscible. Data is as follows:
Property
melting point (K)
molar liquid volume (cm3/mol)
Enthalpy of fusion (J/mol)
Molar liquid volume (cm3/mol)
Benzene
278.7
89
9843
89
n‐Heptane
182.6
148
14067
148
In this system the activity coefficients in the liquid phase are given by:
where 2 is the volume fraction of component 2, and
Problem 4. A liquid mixture contains 5mol% naphthalene and 95 mol % benzene. The mixture is slowly
cooled at constant pressure. At what temperature does a solid phase appear? Assume ideal mixing in
the liquid phase and total immiscibility in the solid phase. Data are:
Property
Melting temperature (K)
Enthalpy of fusion (J/mol)
benzene
278.7
9843
naphthalene
353.4
19008